Simply type "veconlab" into google. The first link shown will be for the instructor to start an experiment. The second is for participating students to log in. You will need a log-in name.
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We see examples of behavioral economics more than we think in our day-to-day lives. How do these principles impact us?
Read the first post in this series, “ Q&A: Behavioral Economics 101 ”, to hear from Dr. Elizabeth Schwab on an overview of behavioral economics.
Read the third post in this series, “ Must-see media list for behavioral economics ” to discover a list of resources to help you learn about the field outside of the classroom.
Our days are a whirlwind of activities—rushing from work, to the gym, to the store, and filling our time with errands, meals, and whatever else we need to do before we start all over again the next day. We are so absorbed in our routines that it’s difficult to have an awareness of the factors that influence us. Behavioral economics is so applicable because it explains some of our behavior that we don’t think twice about.
In this post, we explore these questions: what is behavioral economics? How is it that we encounter this psychological phenomenon daily without recognizing it? What are some examples of behavioral economics?
Behavioral Economics is a study that intersects the teachings of psychology and economics. More specifically, as stated by Investopedia , behavioral economics “relates to the economic decision-making processes of individuals and institutions.”
Behavioral economics principles have major consequences for how we live our lives. By understanding the impact they have on our behavior, we can actively work to shape our realities.
Example #1: playing sports.
Principle : Hot-Hand Fallacy —the belief that a person who experiences success with a random event has a greater probability of further success in additional attempts.
Example : When basketball players are making several shots in a row and feel like they have a “hot hand” and can’t miss.
Relation to BE : Human perception and judgment can be clouded by false signals. There is no “ hot hand ”—it’s just randomness and luck.
Principle : Self-handicapping —a cognitive strategy where people avoid effort to prevent damage to their self-esteem.
Example : In case she does poorly, a student tells her friends that she barely reviewed for an exam, even though she studied a lot.
Relation to BE : People put obstacles in their own paths (and make it harder for themselves) in order to manage future explanations for why they succeed or fail.
Principle : Anchoring —the process of planting a thought in a person’s mind that will later influence this person’s actions.
Example : Starbucks differentiated itself from Dunkin’ Donuts through their unique store ambiance and product names. This allowed the company to break the anchor of Dunkin’ prices and charge more.
Relation to BE : You can always expect a grande Starbucks hot coffee ( $2.10 ) to cost more than a medium one from Dunkin ( $1.89 ). Loyal Starbucks consumers are conditioned, and willing, to pay more even though the coffee is more or less the same.
Principle : Gambler’s Conceit —an erroneous belief that someone can stop a risky action while still engaging in it.
Example : When a gambler says “I can stop the game when I win” or “I can quit when I want to ” at the roulette table or slot machine but doesn’t stop.
Relation to BE : Players are incentivized to keep playing while winning to continue their streak and to keep playing while losing so they can win back money. The gambler continues to perform risky behavior against what is in this person’s best interest.
Principle : Rationalized Cheating —when individuals rationalize cheating so they do not think of themselves as cheaters or as bad people.
Example : A person is more likely to take pencils or a stapler home from work than the equivalent amount of money in cash.
Relation to BE : People rationalize their behavior by framing it as doing something (in this case, taking ) rather than stealing . The willingness to cheat increases as people gain psychological distance from their actions.
These behavioral economics principles have major consequences on how we live our lives. By understanding the impact they have on our behavior, we can actively work to shape our own realities.
As Dan Ariely, Ph.D ., says in his book, “ Predictably Irrational: The Hidden Forces That Shape Our Decisions , ,” “We usually think of ourselves as sitting in the driver’s seat, with ultimate control over the decisions we made and the direction our life takes; but, alas, this perception has more to do with our desires—with how we want to view ourselves—than with reality.”
Awareness of behavioral economics helps us comprehend our actions so we can make better choices and live our lives in the driver’s seat.
For more, see the first blog in this series, a Q&A with Elizabeth Schwab , Psy.D., Associate Department Chair for Business Psychology and Program Chair for Behavioral Economics.
Learn more about our online masters in behavioral economics here and must-see media options for behavioral economics here , or fill out the form below for more information.
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Natural Experiments vs. Controlled Experiments
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A natural experiment is an empirical or observational study in which the control and experimental variables of interest are not artificially manipulated by researchers but instead are allowed to be influenced by nature or factors outside of the researchers' control. Unlike traditional randomized experiments, natural experiments are not controlled by researchers but rather observed and analyzed.
So if natural experiments are not controlled but rather observed by researchers, what is there to distinguish them from purely observational studies? The answer is that natural experiments still follow the primary principles of experimental study. Natural experiments are most effective when they mimic as closely as possible the existence of test and control groups of controlled experiments, which is to say that there is a clearly defined exposure to some condition in a clearly defined population and the absence of that exposure in another similar population for comparison. When such groups are present, the processes behind natural experiments are said to resemble randomization even when researchers do not interfere.
Under these conditions, observed outcomes of natural experiments can feasibly be credited to the exposure meaning that there is some cause for belief in a causal relationship as opposed to simple correlation. It is this characteristic of natural experiments — the effective comparison that makes a case for the existence of a causal relationship — that distinguishes natural experiments from purely non-experimental observational studies. But that is not to say that natural experiments aren't without their critics and validation difficulties. In practice, the circumstances surrounding a natural experiment are often complex and their observations will never unequivocally prove causation. Instead, they provide an important inferential method through which researchers can gather information about a research question upon which data might otherwise not be available.
In the social sciences, particularly economics, the expensive nature and limitations of traditionally controlled experiments involving human subjects has long been recognized as a limitation for the development and progress of the field. As such, natural experiments provide a rare testing ground for economists and their colleagues. Natural experiments are used when such controlled experimentation would be too difficult, expensive, or unethical as is the case with many human experiments. Opportunities for natural experimentation are of the utmost importance to subjects like epidemiology or the study of health and disease conditions in defined populations in which experimental study would problematic, to say the least. But natural experiments are also used by researchers in the field of economics to study otherwise difficult to test subjects and are often possible when there is some change in law, policy, or practice in a defined space like a nation, jurisdiction, or even social group. Some examples of economics research questions that have been studied through natural experimentation include:
If you don't find the experiment you need, consider designing your own !
Economists have written a large number of classroom experiments and published them in a wide variety of books, journals and websites .
Results 1 - 10 of 11 matches
Penalty Kicks—A Simultaneous Move Zero-Sum Game Christina Robinson, Central Connecticut State University Penalty Kicks—A Simultaneous Move Zero-Sum Game is an experiment that illustrates the importance of playing randomized strategies. This experiment is appropriate for undergraduate students who have completed a basic game theory module and can be completed in 15-20 minutes. Subject: Economics: Economics
An Interactive Introduction to Randomized Control Trials Utteeyo Dasgupta, Franklin and Marshall College This activity provides a classroom impact evaluation exercise that serves as an introduction to the primary investigative tool of current Development economics. Subject: Economics: Economics
The Value of Exchange: A Classroom Experiment Tisha Emerson, Baylor University This experiment illustrates the value of exchange to students through trading of candy. Subject: Economics: Economics
Airplane Production: A Law of Diminishing Marginal Product Exercise Tisha Emerson, Baylor University Classroom experiment illustrating the law of diminishing marginal productivity through the production of paper airplanes. Subject: Economics: Economics
Public Goods Experiment Todd Swarthout, Georgia State University Subject: Economics: Economics
Introduction of Backward Induction Technique Using a Classroom Experiment Utteeyo Dasgupta, Franklin and Marshall College This classroom activity serves as an intuitive introduction to backward induction solutions in an upper level undergraduate game theory course. Subject: Economics: Economics
Energy and the Environment Sheryl Ball, Virginia Polytechnic Institute and State Univ This experiment illustrates how seemingly harmless individual actions can, when taken collectively, develop into larger costs to society. Subject: Economics: Economics
Homegrown Demand Todd Swarthout, Georgia State University The professor sells an announced number of M&M packets (or other inexpensive good) through an auction to derive a classroom demand schedule. The resulting demand schedule is displayed as a "curve" and facilitates discussion of consumer demand. Subject: Economics: Economics
Foreign Exchange Rates: Solidifying a Student's Grasp of Supply and Demand Todd Easton, University of Portland In this assignment, students think about four events that would affect a country's exchange rate. Without actually drawing a supply and demand diagram, students say what direction, if at all, each curve would shift--and whether the currency would appreciate or depreciate as a result. Subject: Economics: Economics
Teaching Case: This American Life Episode 391: More is Less, 2009 Christina Robinson, Central Connecticut State University This case study is based on NPR's This American Life Episode 391: More is Less, which originally aired in 2009. The story highlights the role health care providers, patients, and health insurance companies play in driving up the cost of care. Subject: Economics: Economics
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Scott Horsley
Displayed is a file photo of a Nobel Prize medal on Dec. 8, 2020. The Nobel Prize in economic sciences was awarded to three U.S-based professors for their pioneering work with "natural experiments." Jacquelyn Martin/AP hide caption
Displayed is a file photo of a Nobel Prize medal on Dec. 8, 2020. The Nobel Prize in economic sciences was awarded to three U.S-based professors for their pioneering work with "natural experiments."
Three U.S.-based economists will share this year's Nobel Memorial Prize in Economic Sciences for their innovative work with "natural experiments" – events or policy changes in real life that allow researchers to analyze their impact on society.
David Card of the University of California at Berkeley will receive half the prize, worth 10 million Swedish kronor, or about $1.1 million, the Royal Swedish Academy of Sciences said on Monday . Joshua Angrist of the Masschusetts Institute of Technology and Guido Imbens of Stanford University will share the other half.
Controlled experiments are common in science and medicine: they allow, for example, to test new drugs by carefully selecting participants and controlling vital aspects to ensure objectivity.
But they are harder in social sciences where it can often be impractical or unethical to conduct randomized trials – unless a real-life event or policy change happens that allow researchers to conduct what are called "natural experiments."
"Natural experiments are everywhere," said Eva Mork, a member of the prize committee. "Thanks to the contributions of the laureates, we researchers are today able to answer key questions for economic and social policy. And thereby the laureates work has greatly benefited society at large."
The Nobel Economics Prize committee members announce the winners of Nobel Memorial Prize in Economic Sciences on Monday. David Card, Joshua Angrist and Guido Imbens were given the award for their research of real-life events and policy changes. Claudio Bresciani/TT News Agency/AFP via Getty Images hide caption
The Nobel Economics Prize committee members announce the winners of Nobel Memorial Prize in Economic Sciences on Monday. David Card, Joshua Angrist and Guido Imbens were given the award for their research of real-life events and policy changes.
Card was recognized in part for his groundbreaking work in the early 1990s with the late Princeton economist Alan Krueger, which challenged conventional wisdom about minimum wages.
Economists had long assumed that there was a tradeoff between higher wages and jobs. If the minimum wage went up, it was thought, some workers would get higher pay but others would be laid off.
But when Card and Krueger looked at the actual effect of higher wages on fast food workers , they found no significant drop in employment.
They reached this conclusion by comparing fast food restaurants in New Jersey, which raised its minimum wage, with restaurants in neighboring Pennsylvania, which did not.
A McDonald's sign is shown on July 28 in Houston, Texas. One of the winners of the Nobel Prize in economics on Monday was cited for his work in studying the fast food industry to help determine how minimum wages impact employment. Brandon Bell/Getty Images hide caption
A McDonald's sign is shown on July 28 in Houston, Texas. One of the winners of the Nobel Prize in economics on Monday was cited for his work in studying the fast food industry to help determine how minimum wages impact employment.
Meanwhile, Angrist and Imbens were recognized for methodological research that helps tease out cause and effect from these accidental case studies.
During the pandemic, natural experiments have allowed researchers to study the effects of mask mandates, social distancing policies, and supplemental unemployment benefits.
Imbens said he was "stunned" to get the congratulatory wake-up call at about 2 a.m. in California.
"I was absolutely thrilled to hear the news," Imbens told reporters. "In particular hearing that I got to share this with Josh Angrist and David Card, who are both very good friends of mine."
He noted that Angrist was best man at his wedding.
Imbens said he had no idea how he would spend his share of the prize money.
Behavioral experiments in health economics.
The state-of-the-art literature at the interface between experimental and behavioral economics and health economics is reviewed by identifying and discussing 10 areas of potential debate about behavioral experiments in health. By doing so, the different streams and areas of application of the growing field of behavioral experiments in health are reviewed, by discussing which significant questions remain to be discussed, and by highlighting the rationale and the scope for the further development of behavioral experiments in health in the years to come.
In the past few decades, experiments have been successfully introduced in many fields of economics, such as industrial organization (e.g., Chamberlin, 1948 ; Sauermann & Selten, 1959 ; Plott, 1982 ), labor economics (e.g., Fehr, Kirchsteiger, & Riedl, 1993 ; Kagel, Battalio, Rachlin, & Green, 1981 ), and public economics (e.g., Andreoni, 1988 ; Bohm, 1984 ; Marwell & Ames, 1981 ). Despite the fact that the use of experiments was first advocated by leading health economists long ago (Frank, 2007 ; Fuchs, 2000 ; Newhouse et al., 1981 ), their introduction and employment has been relatively slow to be widely accepted in health economics, policy, and management.
Recently, however, two special issues in the Journal of Economic Behavior & Organization (Cox, Green, & Hennig-Schmidt, 2016 ) and in Health Economics (Galizzi & Wiesen, 2017 ) and a number of dedicated special sessions in major field conferences (e.g., the European Association of Health Economics, EuHEA, the International Health Economics Association, iHEA) indicate the increasing acceptance of experiments by the health economics, policy, and management communities.
The rise in interest in using experiments in health economics has coincided with the parallel growing interest in applying behavioral economics to health, as witnessed by an increasing number of books and articles on the topic (Bickel, Moody, & Higgins, 2016 ; Hanoch, Barnes, & Rice, 2017 ; Loewenstein et al., 2017 ; Roberto & Kawachi, 2015 ).
Among health policymakers and practitioners, the use of insights from behavioral economics, and, in particular, of “nudges” has recently led many governments around the world to set up behavioral or “nudge units” within their civil services, starting from the Behavioural Insights Team in the UK Cabinet Office, to the analogous initiatives within the UK Department of Health, the National Health Service (NHS), and Public Health England, in the governments of Australia, Canada, Denmark, Finland, France, Israel, Italy, the Netherlands, New Zealand, Norway, Singapore, and the United States, and in the European Commission (Dolan & Galizzi, 2014a ; Oliver, 2017 ; Sunstein, 2011 ).
We start with a simple operational definition of “behavioral experiments in health,” arguably the first such definition. We then identify ten key areas of potential debate about behavioral experiments in health that we think deserve explicit discussion. In what follows, we address one by one each of these ten areas of possible debate and controversy by answering ten corresponding questions. By doing so, we review the state of the art of the different streams and areas for applications of the growing field of behavioral experiments in health; we discuss which significant questions remain to be addressed; and we highlight the rationale and the scope for the further development of behavioral experiments in health in the years to come.
In a nutshell, “behavioral experiments in health” make use of a broad range of experimental methods typical of experimental and behavioral economics to investigate individual and organizational behaviors and decisions related to health and healthcare.
The behaviors and decisions considered in behavioral experiments in health therefore usually take place, or are framed, in a health, healthcare, or medical setting or context.
The term behavioral in “behavioral experiments in health” first requires a clarification. Common to experimental economics and behavioral science, the outcomes of behavioral experiments in health are “behavioral” in that they consist of directly observable and measurable behavioral responses or directly revealed preferences, rather than self-reported statements. For example, subjects in behavioral experiments in health are typically observed in real health or healthcare field situations, or, if not, they face real consequences for their choices or behaviors through aligned monetary and nonmonetary incentives. Behaviors and decisions of participants in a behavioral experiment in health are thus typically “natural”—that is they take place in naturalistic situations—or “incentive-compatible” in the usual experimental economics sense that participants bear some real behavioral consequences for their choices in the experiment (e.g., Cassar & Friedman, 2004 Friedman & Sunder, 1994 ; Smith, 1976 , 1982 ). This defining feature makes behavioral experiments in health distinct from “stated preference experiments,” such as contingent valuation studies, or “discrete choice experiments” (DCEs), which have long been used in health economics, and which do not typically consider real behavior or incentive-compatible choice situations (e.g., de Bekker-Grob, Ryan, & Gerard, 2012 ; Ryan & Farrar, 2000 ; Ryan, McIntosh, & Shackley, 1998 ).
Furthermore, methodologically, behavioral experiments in health purportedly cover the entire continuum spectrum of experimental methods spanning the lab to the field, passing through online and mobile experiments, and experiments pursuing “behavioral data linking” (for more, see Questions Three and Ten).
Finally, and following the usual methodological convention in experimental economics, behavioral experiments in health do not deceive subjects. Some behavioral experiments in health can, nonetheless, entail some degree of “obfuscation” when, in the attempt to minimize possible “experimenter demand effects” (Zizzo, 2010 ), subjects are not told about the exact purpose and research question of the experiment. This is in line with the spirit of those experiments that intend to minimize the alteration of, and interference with, naturally occurring behavior by not telling subjects that they are part of an experiment (i.e., in the spirit of “natural field experiments” according to the taxonomy by Harrison & List, 2004 , discussed in Question Three; or of “lab-field” experiments, as in Dolan & Galizzi, 2014a ).
To sum up, five characterizing features of behavioral experiments in health are therefore: (i) the fact that the decisions and behaviors are health-related; (ii) the fact that, whenever possible, the outcomes of the decisions in the experiment are “behavioral” in the sense of consisting of directly observable and measurable behavioral responses, or of bearing real consequences for the decision makers; (iii) the open-minded consideration of principles and insights from both behavioral economics and conventional economics, as well as their combination and integration; (iv) the use of a broad range of experiments spanning the lab to the field, passing through online and mobile experiments, as well as “behavioral data linking” experiments; and (v) the tendency to avoid deception, which, however, does not prevent the use of obfuscation, natural field experiments, and lab-field experiments.
We next review the existing literature by addressing ten areas of current debate about behavioral experiments in health. A few of these areas apply to behavioral experiments more generally and, when this is the case, we explicitly note it.
First of all, theory, experiments, and econometrics are complements to, not substitutes for, each other (Falk & Heckman, 2009 ; Galizzi, Harrison, & Miraldo, 2017b ); Harrison, Lau, & Rutström, 2015 . In particular, the way in which behavioral experiments are sometimes contrasted with econometric analysis is misleading. In fact, running any type of controlled behavioral experiments in health (see more in question three) is just the first step of the data collection process that should then feed into an appropriate econometric analysis of the experimental data. The broad range of behavioral experiments in health allows the researcher to gather rich data to delve empirically into the behavioral nuances and mechanisms of an observed change in health-related behavior. Indeed, as witnessed by the field of “behavioral econometrics,” experiments and econometric analysis are complementary, not substitute, methods (Andersen, Harrison, Lau, & Rutström, 2008a , 2010 , 2014 ; Harrison, Lau, & Rutström, 2015 ; Hey & Orme, 1994 ). A similar point holds for the theoretical underpinnings of a behavioral experiment in health.
Second, a key advantage of behavioral experiments is the ability to tightly control experimental conditions. In physics and social sciences, testing theory is a basic component of experiments and the scientific method relies upon explicit tests of theory (Charness & Fehr, 2015 ; Charness & Kuhn, 2011 ). While secondary data are often rich and abundant, at the same time they might be confounded by a variety of environmental factors. For example, a health economist who aims to test the effect of incentives inherent in performance pay on the physicians’ quality of medical care using secondary data might end up with confounded results because institutions such as public monitoring and reporting of physicians’ quality were introduced at the same time. Using secondary data, disentangling these factors seems prohibitively challenging, if not impossible. Taking a more general perspective, the key strength of behavioral experiments is the ability to test a specific theoretical model. One can then compare the behavioral predictions of the model to what happens. If a specific theory is rejected, it is then relatively neat to test competing explanations. For example, rational decision-making theory might not be suitable to explain the inconsistent choices of insurance plans in the United States (e.g., Abaluck & Gruber, 2011 ). Competing behavioral decision-making theories might then be called upon whose alternative explanations can then be tested in controlled experiments. This is consistent with the open-minded approach of behavioral experiments in health, which consider principles and insights from both behavioral economics and conventional economics.
Third, another reason to run experiments is the unique opportunity to study behavior and practices analyzed in the theoretical health economics models that are difficult to observe using field data. An example is the effect of referral payments from specialists to primary care physicians on primary care physicians’ referral behavior. While health economic theory (e.g., Pauly, 1979 ) suggests that referral fees enhance efficiency, payments for referrals are largely forbidden, in almost all Western healthcare markets. In a lab experiment, Waibel and Wiesen ( 2017 ) explicitly test model predictions on physicians’ diagnostic effort and referral decisions and find that the introduction of referral payments increase efficiency, although not to the levels predicted by theory. Another example is unethical behavior in healthcare, for example, diagnosis-related group (DRG) upcoding. Admittedly, at an aggregate level there is plenty of evidence that DRG upcoding exists (e.g., Jürges & Köberlein, 2015 ; Silverman & Skinner, 2004 ). However, what drives unethical behaviors is largely unknown. A study by Hennig-Schmidt, Jürges, and Wiesen ( 2017 ) complements field studies on DRG upcoding by analyzing dishonest behavior in a framed experiment in neonatology and by linking dishonest behavior to individuals’ characteristics to explore what drives dishonesty. They find that audits and fines significantly reduce dishonesty and that subjects’ personality traits and integrity relate to dishonest behavior. A further area in health, to which behavioral experiments have contributed, is a better understanding of the behavioral effects of professional norms. Exogenously changing professional norms in the field seems prohibitively challenging, and (if possible) drawing inferences seems difficult due to numerous confounding factors. In an online experiment with a large medical student sample, Kesternich, Schumacher, and Winter ( 2015 ) analyze the effect of making the Hippocratic oath salient on patient-regarding altruism and distributional preferences. In a series of experiments with physicians (from internal medicine and pediatrics), Ockenfels and Wiesen ( 2018 ) investigate the effect of a professional framing on physicians’ dishonest behavior (on behalf of themselves and others). Evidence from behavioral experiments in health that are “well-grounded” in theory is therefore not only useful to contrast behavior with model predictions but also to further stimulate the debate among healthcare policymakers on practices with little or no field evidence.
Fourth, one of the key strengths of experiments, in general, is that a researcher can empirically study the causal effects of different institutions, as defined by their rules, actors, and incentives. Thus, behavioral experiments seem ideal to serve as a test bed for analyzing the effect of institutional changes related to healthcare. Understanding behavioral mechanisms in health-related decisions is imperative before designing and implementing large-scale behavioral interventions in the field or ad hoc healthcare policy interventions, as there might be unknown or unintended effects for providers and patients alike. In this sense, excluding behavioral experiments from the research toolkit of a health economist would be somewhat similar to ignoring animal studies for medical or drug research:
While results from animal studies do not always apply to humans, the ability to test many hypotheses cheaply under carefully controlled conditions provides an indispensable tool for the development of models that work in the real world. (Charness & Kuhn, 2011 , p. 233)
Fifth, behavioral results from experiments might not only be insightful to better understand actual health-related decision-making and behavior, but also to inform the development of behavioral economics theories in health contexts (e.g., Hansen, Anell, Gerdtham, & Lyttkens, 2015 ; Kőszegi, 2003 , 2006 ; Frank, 2007 ). The observation of actual human behavior in experiments enables the researcher to identify behavioral deviations from theory and thus to extend health economic theories by taking into account issues like human motivation or behavioral phenomena like emotions or (patient-regarding) altruism. Two prominent research areas in which theory and experiments have already fruitfully complemented each other are: the matching markets for organ donations and for physicians and healthcare professionals (e.g., Herr & Normann, 2016 ; Kessler & Roth, 2012 , 2014a , 2014b ; Li, Hawley, & Schnier, 2013 ; Roth, 2002 ; Roth & Peranson, 1999 ); and the design of mixed systems of public and private healthcare finance (e.g., Buckley et al., 2012 , 2016 ).
In sum, running behavioral experiments in health allows the researcher to better understand the causal effects of health-related policy interventions on individual and organizational behavior and to contrast findings with predictions from theoretical models. Behavioral experiments therefore nicely complement and bridge non-experimental methods, in particular theory and empirical econometric analysis, and could therefore help bring closer together the different health research communities (Galizzi, 2017 ; Galizzi, Harrison, & Miraldo, 2017 ).
No. First, health economists are particularly well aware of the importance of using randomized controlled experiments. Modern evidence-based medicine and pharmacology are all based on randomized controlled trials (RCTs), starting from the pioneering work on scurvy by James Lind in 1747 , to the first published RCT in medicine by Austin Bradford Hill and colleagues in 1948 . Thanks to the groundbreaking contributions of Charles Sanders Peirce, Jerzy Neyman, Ronald A. Fisher, and others, modern science has long considered randomized controlled experiments as fundamental and important scientific methods. Far from novel, the idea of using randomized controlled experiments has been advocated for decades even for policy applications (Burtless, 1995 ; Ferber & Hirsch, 1978 ; Rubin, 1974 ).
Second, arguably one of the most influential studies in health economics is indeed based on a large-scale randomized controlled experiment. The RAND Health Insurance Experiment conducted in the United States between 1974 and 1982 , in fact, analyzed the effects of randomly allocated co-payment rates and health insurance contracts on healthcare costs and utilization of healthcare (Manning et al., 1987 ; Newhouse et al., 1981 ). As a major finding, Joseph P. Newhouse and colleagues documented that cost sharing reduced the overutilization of medical care while it did not significantly affect the quality of care received by participating patients.
The spirit and the main features of the RAND Health Insurance Experiment later inspired the design of the Oregon Health Insurance Experiment. The latter was conducted in 2008 with uninsured low-income adults in Oregon. Adults allocated to the treatment group were given the chance to apply for Medicaid (via a lottery). This allowed researchers to analyze the effects of expanding access to public health insurance (Medicaid), for example, on the healthcare use and health of low-income adults. The researchers found that the treatment group had substantively and statistically significantly higher healthcare utilization and a better self-reported health than the control group (Finkelstein et al., 2012 ; Finkelstein & Taubman, 2015 ).
The launch of the Behavioural Experiments in Health Network (BEH-net) in 2015 can be seen as the response to a fast-increasing demand to systematically use behavioral experiments in health economics, policy, and management. The network aims precisely at integrating and bringing closer together the research communities at the interface between experimental and behavioral economics, and health economics.
There is an important initial conceptual distinction between behavioral experiments in health and RCTs. Many health practitioners and policymakers, in fact, tend to automatically associate behavioral experiments with RCTs.
In the health policy debate, the term RCT is sometimes used to denote large-scale field experiments conducted with entire organizations (e.g., hospitals, villages) without necessarily allowing the stakeholders in those organizations to explicitly express their views or their consent to the proposed manipulations. This is a major conceptual and practical difference with respect to proper RCTs in medicine or pharmacology, where subjects are always explicitly asked to give informed consent prior to taking part in RCT, and are allowed to drop out, with important ethical, political, and logistical implications. The term RCT is therefore conceptually inappropriate and practically misleading in a health economics, policy, and management context, since it conveys the false impression that subjects have been made aware of being part of an experiment and have been consulted and given their consent to it, when actually this may not be the case.
Moreover, even in the above narrow and inappropriate connotation, RCTs are only one specific type of experiment, namely field experiments. As mentioned, however, behavioral experiments in health purportedly cover the entire spectrum of experiments from the lab to the field. Harrison and List ( 2004 ) proposed an influential taxonomy of experiments along the lab-field spectrum that illustrates the diversity of experiments: (i) conventional lab experiments involve student subjects, abstract framing, a lab context, and a set of imposed rules; (ii) artefactual field experiments depart from conventional lab experiments in that they involve nonstudent samples; (iii) framed field experiments add to artefactual field experiments a field context in the commodity, stakes, task, or information; and, finally, (iv) natural field experiments depart from framed field experiments in that subjects undertake the tasks in their natural environment and subjects do not know that they are taking part in an experiment.
The main idea behind natural field experiments is equivalent to von Heisenberg’s “uncertainty principle” in physics: the mere act of observation and measurement necessarily alters, to some extent, what is being observed and measured. In key areas for health economics, for example, there may be potential experimenter demand effects, where participants change behavior due to cues about what represents “appropriate” behavior for the experimenter (Levitt & List, 2007 ), for example, when deciding on provision of medical services; Hawthorne effects, where simply knowing they are part of a study makes participants feel important and improves their effort and performance (Levitt & List, 2011 ); and John Henry effects, where participants who perceive that they are in the control group exert greater effort because they treat the experiment like a competitive contest and they want to overcome the disadvantage of being in the control group (Cook & Campbell, 1979 ).
More recently, other types of experiments have been conducted in experimental economics, beyond lab, artefactual field, frame field, and natural field experiments. For example, virtual experiments combine controlled experiments with virtual reality settings (Fiore, Harrison, Hughes, & Rutström, 2009 ). While not yet applied to health economics contexts, virtual experiments are a promising approach to make trade-offs more salient and vivid in health and healthcare decision-making.
Lab-field experiments consist of a first-stage intervention under controlled conditions (in the lab) linked to a naturalistic situation (in the field) where subjects are not aware that their behavior is observed. Lab-field experiments have been used to look at the unintended “behavioral spillover” effects of health incentives (Dolan & Galizzi, 2014b , 2015 ; Dolan, Galizzi, & Navarro-Martinez, 2015 ) or at the external validity of lab-based behavioral measures (Galizzi & Navarro-Martinez, 2019 ).
Virtual experiments and lab-field experiments are part of the growing efforts to bridge the gap between the lab and the field in health economics applications (Hennig-Schmidt, Selten, & Wiesen, 2011 ; Kesternich et al., 2015 ). They are also part of the more general “behavioral data linking” approach (Galizzi, Harrison, & Miraldo, 2017 ), that is, the linkage of behavioral economics experiments with longitudinal surveys, administrative registers, biomarkers banks, apps, mobile devices, scan data, and other big data sources (Andersen et al., 2015 ; Galizzi, Harrison, & Miniaci, 2017 ). Data linkage poses new ethical, practical, and logistical challenges when it seeks to link surveys and behavioral experiments with health records and healthcare registers (Galizzi, Harrison, & Miraldo, 2017 ). Nonetheless, there is currently an extraordinary, and still largely untapped, potential to apply the experimental approach to an unprecedented host of health and healthcare contexts, and by linking and augmenting behavioral experiments in health with the very rich data sources available in health (see more in Question Ten).
Taken together, there is not one type of experiment for potential health economics and policy purposes. Rather, the broad spectrum of different types of experiments spanning the lab to the field can prove useful and complementary for health applications, as well as the most recent online, mobile, and “behavioral data linking” experiments.
There is currently no consensus on which specific type of behavioral experiment is superior. The choice of the specific type of experiment depends on the specific research question. Lab, field, online, mobile, and “behavioral data linking” experiments all have strengths and weaknesses, and their relative merits have been systematically discussed elsewhere (Bardsley et al., 2009 ; Falk & Heckman, 2009 ; Guala, 2005 ; Harrison, 2013 ; Harrison & List, 2004 ; Kagel, 2015 ; Levitt & List, 2007 , 2009 ; Smith, 2002 ).
For example, it is generally reckoned that lab experiments allow for high internal validity because of their ability to tightly control the environment and frame, to minimize confounding factors, to closely simulate conditions of theoretical models, and to replicate past experiments. Furthermore, they provide insights into possible patterns prior to moving into the field, they uncover the mechanisms underlying decisions and behavior, and they require significantly fewer financial, time, and logistical resources than field experiments.
On the other hand, it is generally reckoned that field experiments can enhance the external validity of experimental results (see more about this in Question Five), because observations are made with subjects, environments, situations, tasks, rules, and stakes that are closer to the ones occurring in the real world (Brookshire, Coursey, & Schulze, 1987 ; Galizzi & Navarro-Martinez, 2019 ). Field experiments, however, come with less control and with several other limitations when used for policy purposes (Harrison, 2014 ). Moreover, they are inherently more difficult to replicate. This is a major limitation given the increasing attention to the replicability of experimental results in economics, psychology, and health sciences (Burman, Reed, & Alm, 2010 ; Camerer et al., 2016 ; Dolan & Galizzi, 2014a ; Galizzi, Harrison, & Miraldo, 2017 ; Open Science Collaboration, 2015 ).
More generally, it is important to reiterate the point that the different types of experiments are complementary, not substitutes (Falk & Heckman, 2009 ; Galizzi, Harrison, & Miraldo, 2017 ; Harrison, Lau, & Rutström, 2015 ). Recent behavioral experiments in health pick up on this important point and combine different types of experiments and thereby test for the validity of findings from lab experiments with conventional student samples. For example, Brosig-Koch, Hennig-Schmidt, Kairies-Schwarz, and Wiesen ( 2016a ) combine lab and artefactual field experiments to analyze the effect of fee-for-service and capitation regimes for medical service provision on the behaviors of medical students, nonmedical students, and physicians. Across the board, they found that all subject pools responded to incentives similarly—namely, patients were overtreated under fee-for-service and undertreated under capitation. Physicians, however, responded less to the incentives inherent in these two payment schemes. In experiments with medical and non-medical students, Hennig-Schmidt and Wiesen ( 2014 ) and Brosig-Koch, Hennig-Schmidt, Kairies-Schwarz, and Wiesen ( 2017a ) report similar findings. Wang, Iversen, Hennig-Schmidt, and Godager ( 2017 ) compare behavior of physicians and medical students in China and Germany. Comparing lab experimental data from medical students with artefactual field experimental data from a subsample of a representative sample of German resident physicians, Brosig-Koch, Hennig-Schmidt, Kairies-Schwarz, and Wiesen ( 2017b ) find that performance pay crowds out patient-regarding motivation for both subject pools.
Taken together, the experimental studies that systematically account for potential differences in the subject pools indicate that the direction of a treatment effect does not differ between (medical or nonmedical) students and medical professionals. Importantly, however, the intensity of a behavioral effect might vary across subject pools. Moreover, experimental designs in health typically abstract from the complexity of real-world settings in order to “isolate” treatment effects. A few experimental studies even employ neutral framings of the decision situation, presumably for reasons of control and salience of the incentives: see, for example, Green ( 2014 ) on provider incentives; Huck, Lünser, Spitzer, and Tyran ( 2016 ) on health insurance choice; and Mimra, Rasch, and Waibel ( 2016 ) on specialists’ second opinions. As experiments are “scalable,” adding more realism (health context) to these settings by employing medical frames seems desirable: Ahlert, Felder, and Vogt ( 2012 ) and Kesternich et al. ( 2015 ) find behavioral differences in the intensity of subjects’ responses when comparing neutral and medical frames.
In sum, researchers and healthcare policymakers alike might clearly need to be cautious in drawing conclusions about real-world settings when taking findings from behavioral experiments in health at face value. One might argue, however, that this key point applies to any type of behavioral experiments in health, not just to lab experiments or to field experiments. Moreover, the existing evidence indicates somewhat similar main directions of experimental treatment effects across subject pools and it is therefore useful to inform debates in healthcare policy and management. For a more general discussion of external validity and generalizability of experimental findings, see the next question.
The point on the external validity of behavioral experiments in health is too important to be unduly misrepresented or oversimplified, as is often done in the research and policy debate. Most issues related to the external validity of experiments are actually not unique to behavioral experiments in health, but are common to all the economic experiments in general, and for this reason we answer this question more generally.
The main observation is that external validity means different things from different points of view. In a first connotation, external validity refers to the within-subjects question of whether the outcomes of a behavioral experiment in health are representative of the corresponding outcomes of interest that would occur outside of the behavioral experiment for the same pool of subjects. From this perspective, as mentioned, external validity is often contrasted with internal validity on the presumed ground that there is always an inherent trade-off between internal and external validity while one moves from the lab end to the field end of the spectrum in the Harrison and List ( 2004 ) taxonomy. This, however, is not always nor necessarily the case. In fact, to start with, if rigorously designed and conducted, all randomized controlled behavioral experiments in health are internally valid, whether they are lab, artefactual field, framed field, or natural field experiments. So, it is simply not true that internal validity is necessarily higher in lab than in natural field experiments. Moreover, it is also not true that the external validity (in the above explained connotation) is necessarily higher in natural field than in lab experiments. It obviously depends on how close is the correspondence between the outcomes measured in the behavioral experiment and the outcomes of interest that would occur outside of the behavioral experiments. In other words, it depends on what the final outcomes of interest are, and ultimately, what the research question is. For example, imagine that the main outcome of interest is about looking at how many calories subjects eat in a buffet, or how much time they wait until lighting up the next cigarette, which are both likely to be the outcomes of some automatic or “visceral” decision-making occurring without any conscious deliberation (Loewenstein, 1996 ). Then, a natural field experiment, where subjects do not know they are part of an experiment, would be a natural setting for observing such behaviors (Dolan & Galizzi, 2014b ). On the other hand, however, imagine that the main outcomes of interest are how subjects trade off and choose between different private health insurance schemes, or which groceries subjects purchase in an online supermarket, two highly deliberate decisions that are both likely to take place in online settings even when they occur outside of a behavioral experiment. Then, a conventional lab or an online experiment would be a natural setting for observing such behaviors.
In a second, slightly different, connotation, external validity refers to the, still within-subjects, question of whether the outcomes of a behavioral experiment in health are good predictors of the corresponding outcomes of interest that would occur outside of the behavioral experiment for the same pool of subjects. For example, are healthy food choices in a behavioral experiment good predictors of a subject’s healthy diet? Are experimental decisions about drugs, treatments, and health insurance good predictors of analogous decisions outside the experiment? It is true that, in principle, the experimental decisions can move closer to the decisions taken outside the experiment as one moves from lab experiments to natural field experiments in the Harrison and List ( 2004 ) taxonomy. But it is also true that this depends, again, on what the ultimate outcomes of interest and research questions are. And also, in principle, this type of external validity question can affect the entire spectrum of behavioral experiments in health, from lab to natural field experiments. In fact, the only rigorous strategy to empirically address this question is to design and implement a longitudinal augmentation of the original behavioral experiment that enables researchers to follow up over time in more naturalistic settings the same pool of subjects. When implemented in a systematic and transparent way, this strategy also allows the researcher to overcome a major limitation of the very few external validity analyses to date, namely the fact that they typically are ad hoc analyses. The typical analysis, in fact, reports the correlation between one specific experimental outcome and one specific variable outside the experiment and, when such a correlation is found to be statistically significant, it concludes that what is found in the experiment is externally valid. Such an approach, however, lacks systematization because it fails to provide full information on the whole set of pairwise correlations between all the experimental outcomes and all the variables outside the experiment, be they significant or not significant. Only a systematic and transparent testing and reporting of all such correlations would be the litmus test of the external validity of a behavioral experiment. Such exercises are rare in experimental economics and virtually not existent in health.
In a nonhealth context, for example, Galizzi and Navarro-Martinez ( 2019 ) systematically assess and report the associations between the whole set of eight social preferences experimental games and five different prosocial variables outside of the experiment, and they find that only one out of 40 pairwise correlations is statistically significant (and none is if there is proper correction for multiple hypothesis testing). They then relate their finding to a systematic review and meta-analysis of all the published and unpublished studies that have previously tested the external validity of those same experimental games, and conclude that the often proclaimed external validity of social preferences games is not supported by the empirical evidence: only the 39.7% of the reported pairwise correlations and 37.5% of the reported regressions find a statistically significant association between an experimental outcome and a variable outside the experiment.
The behavioral experiments in the health literature still lack a similar systematic and transparent approach to this dimension of the external validity question and, given the importance of this exercise for both research and policy purposes, we encourage more research in this direction (Galizzi, Machado, & Miniaci, 2016a ). For example, the lack of transparency and systematization is the main explanation behind the current sterile debate about whether lab-based behavioral economics measures for risk, time, and social preferences are externally valid in the health context. Very few studies in behavioral health economics have tied their hands by publishing a pre-analysis plan or a public protocol that clearly and explicitly states at the outset of the analysis which health behaviors in the field will be associated with the lab-based behavioral economics measures. Most studies only report ad hoc subsets of the correlations and regressions between those measures and the health behaviors, and do not report nor discuss how these results relate and compare to the whole set of statistically significant and not significant associations. Moreover, systematic replication is almost inexistent in behavioral experiments in health. It is even argued by strong proponents of the lab experiments that preferences can only be measured in the lab. This is tantamount to stating that the question of whether lab-based measures for those preferences are externally valid is a non-falsifiable question, which is the opposite of an evidence-based scientific approach to this key matter. If behavioral experiments in health are about to leave infancy for adulthood, they should better take seriously the lessons learned in the neighboring disciplines of medicine and health studies, where collective knowledge is systematically cumulated only through transparent replications, systematic reviews, and meta-analyses, as epitomized by major collective research infrastructures, such as the Cochrane Collaboration or the Campbell Collaboration.
A third connotation of external validity has to do with whether the outcomes of a behavioral experiment in health are representative of the corresponding outcomes of the population of interest. This “out-of-sample” connotation of external validity clearly requires that the pool of subjects involved in the behavioral experiment in health has been drawn from a representative sample of the population of interest. So, for example, if the behavioral experiment aims at concluding something about decisions or behaviors of medical doctors, it should involve a representative sample of medical doctors, while if it aims at inferring anything at a population level, the behavioral experiment should involve a representative sample of the population.
Moreover, the debate about the external validity of behavioral experiments in health should be more generally conducted within the broader framework of the debate in terms of generalizability — that is, the question of which other populations, settings, contexts, or domains the findings from an experiment can be generalized to (Al-Ubaydli & List, 2015 ). Importantly, the generalizability question equally applies to the whole spectrum of behavioral experiments in health, from lab to natural field experiments.
There are three conceptually distinct threats to generalizability of behavioral experiments in health. The first threat comes essentially from participation bias. Unlike natural field experiments, lab, artefactual field, and framed field experiments recruit subjects through an explicit invitation to take part in an experiment. As a result, there is bias because subjects who choose to participate in experiments may be inherently different in their underlying characteristics from subjects who choose not to take part. Health researchers and policymakers should therefore be aware that, because of the participation bias, even if the initial sample of subjects is indeed representative of the target student population, the resulting subsample of actual respondents may not be.
The second threat comes from the fact that the environment, context, and frame of the experimental decisions and tasks in the lab may not be representative of real situations encountered by subjects in natural health and healthcare settings. This limitation can be easily overcome by redesigning tasks and contexts to more closely match naturalistic situations that subjects are more familiar with in real life—that is, to design framed field experiments in the sense of Harrison and List ( 2004 ). This strategy has been extensively employed in other application areas in experimental economics (e.g., Harrison & List, 2008 ; Harrison, List, & Towe, 2007 ) and has already been explored in the health economics area (e.g., Eilermann et al., 2017 ; Hennig-Schmidt et al., 2011 ; Hennig-Schmidt & Wiesen, 2014 ; Galizzi et al., 2016 ).
The last threat to generalizability is that experimental subjects may not be representative of the general population, especially when they are students or medical students (Levitt & List, 2007 ). To overcome this limitation, behavioral economists have started running artefactual field experiments with representative samples of the population (Andersen et al., 2008a , 2014 ; Galizzi, Machado, & Miniaci, 2016 ; Galizzi, Harrison, & Miniaci, 2017 ; Harrison et al., 2007 ; Harrison, Lau, & Williams, 2002 ). This is a promising avenue for behavioral experiments in health, given that the goals and priorities in designing health policies and health systems are typically set at a population level (Michie, 2008 ).
From the broader generalizability perspective, we can hardly see why the results of a natural field experiment with, say, female nurses in Tanzania, or health insurance customers in the rural Philippines, should be considered as more generalizable than a lab experiment with medical students in Germany, or an artefactual field experiment with a representative sample of the population in the United Kingdom. Too often, similar claims even forget to state what the population of interest is for the study.
More generally, Falk and Heckman ( 2009 ) state that causal knowledge requires a controlled variation. Whether a variation from, for example, a natural field experiment or a more controlled lab experiment is more informative depends on the research question and is still debated among researchers in social sciences. It is important to acknowledge, again, that empirical methods and different sources of data are complements. For example, both behavioral experiments, spanning the lab to the field, and econometric analyses of secondary data can all improve the state of knowledge in health economics research, with the issue of generalizability of results being applicable to all of them.
Taken together, behavioral and experimental health economists should take seriously the external validity and generalizability challenges by open-mindedly using all types of experiments in the lab-field spectrum, by embracing a transparent and systematic approach in gathering and reporting evidence, including reporting of all the statistically significant and not significant correlations and regressions (rather than cherry-picked subsets of the positive results). We see this as a fundamental requisite for behavioral experiments in health as a field moving, in the years to come, from infancy to adulthood.
One of the above-discussed defining features of behavioral experiments in health is that they entail directly observable and measurable behavioral responses. For example, experimental decisions, tasks, and measures to elicit preferences and willingness-to-pay are incentive-compatible in the sense that subjects pay some real consequence in terms of monetary or nonmonetary outcomes for the choices they make. This raises the question of whether or not behavioral experiments in health also include the experimental studies that aim at eliciting health-related preferences.
Some distinctions should be made on this point. On the one hand, there is a vast literature in health economics that uses popular experimental methods, such as the Standard Gamble (SG) or the Time Trade Off (TTO), to elicit preferences for hypothetical health states (Attema & Brouwer, 2012 ; Bleichrodt, 2002 ; Bleichrodt & Johannesson, 2001 ). Given the hypothetical nature of the choices about different health states, these experiments are similar in nature to the already discussed “stated preference experiments,” such as contingent valuation studies or discrete choice experiments (DCEs), which do not typically consider real behavior or incentive-compatible choice situations. Using the same argument, therefore, the experiments in this literature should not be considered behavioral experiments in health.
On the other hand, there is also a small, but growing, literature looking at the relationships between incentive-compatible experimental measures of risk and time preferences and health-related behaviors. Harrison, Lau, and Rutström ( 2010 ), for example, elicit risk and time preferences of a representative sample of the Danish population and find no difference in the likelihood of smokers and nonsmokers exhibiting hyperbolic discounting, no significant association of smoking with risk aversion among men, and no significant association of smoking with discount rates among women. Galizzi and Miraldo ( 2017 ) measure the risk preferences of a convenience sample of students and find that, while there is no association between smoking or body mass index (BMI) with the estimated risk aversion, the latter is significantly associated with the Healthy Eating Index, an indicator of overall nutritional quality. Harrison, Hofmeyr, Ross, and Swarthout ( 2015 ) elicit risk and time preferences of a convenience sample of students at the University of Cape Town and find that smokers and nonsmokers differ in their baseline discount rates, but do not significantly differ in their present bias, risk aversion, or subjective perception of probabilities. In a longitudinal experiment with a representative sample of the UK population, Galizzi, Machado, and Miniaci ( 2016 ) systematically assess the external validity of different measures of risk preferences linked to the UK Longitudinal Household Survey (UKHLS), and find that the experimental measures are not significantly associated with subjects’ BMI and eating, smoking, or drinking habits. Several other ad hoc analyses have associated risk and time preferences with heavy drinking (Anderson & Mellor, 2008 ), BMI (Sutter, Kocher, Glätzle-Rützler, & Trautmann, 2013 ), and the uptake of vaccinations, preventive care, and medical tests (Bradford, 2010 ; Bradford et al., 2010 ; Chapman & Coups, 1999 ).
Given that all these latter experiments use incentive-compatible methods to elicit risk and time preferences, they should be considered behavioral experiments in health. A common aspect of the latter group of experiments, however, is that they measure individual risk and time preferences over (risky or intertemporal) monetary outcomes, and then link these to health-related behaviors. But what about the studies that elicit individual risk and time preferences for health outcomes, rather than for monetary outcomes?
We see the experiments eliciting risk and time preferences in health as an interesting middle ground between stated preferences experiments and behavioral experiments. When it comes to the measurement of risk and time preferences in the health domain, in fact, the current community of behavioral health experimentalists interprets behavioral experiments in health with a fair degree of tolerance, flexibility, and open-mindedness, and considers the elicitation of risk and time preferences in health a research field that is closely aligned with, and affine to, the core interests and methods of behavioral experiments in health.
This is not because the community disagrees with the traditional experimental economics view that answers to hypothetical questions can significantly differ from responses to incentive-compatible tests because “talk is cheap” if there are no real behavioral consequences (Battalio, Kagel, & Jiranyakul, 1990 ; Cummings, Elliott, Harrison, & Murphy, 1997 ; Cummings, Harrison, & Rutström, 1995 ; Harrison, 2006 ; Holt & Laury, 2002 ;). Moreover, behavioral health experimentalists are all well aware that, from a theoretical perspective, risk and time preferences are fundamental individual characteristics at the core of health behavior and decision-making (Gafni & Torrance, 1984 ). Risk and time preferences, in fact, directly inform the principles and practices of cost-effectiveness analysis (CEA) and cost-utility analysis (CUA) in healthcare, and the assumptions beyond the quality adjusted life years (QALY), the measure of health benefits that is commonly employed in CEA and CUA and that relies on the above-mentioned SG and TTO methods (Bleichrodt, Wakker, & Johannesson, 1997 ).
Rather, it is because at the moment the literature on behavioral experiments in health lacks a systematic body of state-of-the-art consensus methods to measure health-related preferences with real nonmonetary consequences. Given the fundamental role of risk and time preferences in the health context, it is actually surprising that there is no consensus to date on a “gold standard” measurement methodology.
A multitude of different methods have been proposed to measure risk and time preferences in health contexts, which are heterogeneous in terms of underlying theoretical frameworks, methodological features, and links to formal econometric analysis (Galizzi, Harrison, & Miraldo, 2017 ). A major challenge in converging to a consensus methodology to measure risk and time preferences in health is related to the fact that, to date, the different proposed methods are substantially disconnected. On the one hand, the current methods to measure preferences for health outcomes only entail hypothetical scenarios. On the other hand, all the incentive-compatible methods to measure preferences with real consequences are based on monetary outcomes. From both a conceptual and an empirical point of view, however, it is unclear whether individual risk and time preferences are stable across the health and the monetary domains (Chapman, 1996 ).
There have been a number of exploratory analyses of whether these preferences are indeed stable across the finance and the health domains. Galizzi, Miraldo, and Stavropoulou ( 2016 ), for example, summarize the relatively limited number of studies that compare risk taking across the health and other domains, and find that, despite the broad heterogeneity of methods and frames used in the literature, there is general evidence that there are differences across domains, and that these differences also emerge when real consequences are at stake.
The elicitation of risk and time preferences with incentive-compatible methods in the health domain is a promising and challenging task and a collective priority in the research agenda of behavioral experimentalists in health. We expect this methodological and substantial gap to be filled soon by the increasingly collaborative community of behavioral experimentalists in health.
A first area of experimental research that has recently received considerable attention are “nudges,” that is, changes in the “choice architecture” made to induce changes in health behavior, mainly at an unconscious or automatic level (Thaler & Sunstein, 2008 ). In the spirit of “asymmetric paternalism” (Loewenstein, Asch, & Volpp, 2013 ; Loewenstein, Brennan, & Volpp, 2007 ), many behavioral experiments have in fact applied nudges to health and healthcare behavior spanning from risky behaviors in adolescents (Clark & Loheac, 2007 ) to exercise (Calzolari & Nardotto, 2016 ), from food choices (Milkman, Minson, & Volpp, 2014 ; Schwartz et al., 2014 ; VanEpps, Downs, & Loewenstein, 2016a ; Schwartz, Riis, Elbel, & Ariely, 2012 ; 2016b ) to drugs compliance (Vervloet et al., 2012 ), from medical decision-making (Ansher et al., 2014 ; Brewer, Chapman, Schwartz, & Bergus, 2007 ; Schwartz & Chapman, 1999 ) to dentists’ services (Altman & Traxler, 2014 ).
There is, however, much more in behavioral experiments in health than just nudging (Galizzi, Harrison, & Miraldo, 2017 ; Oliver, 2017 ). Behavioral experiments in health can, in fact, uncover the behavioral mechanisms beyond the change in health behavior, and thus inform the design and the implementation of a series of other types of health policies, including informational campaigns, salient labeling and packaging of healthy food items, the use of financial and nonfinancial incentives, and the design of effective tax, subsidy, health insurance plans, and regulatory schemes (Galizzi, 2014 , 2017 ).
In fact, a broad spectrum of lab to natural field experiments have already been applied to a variety of health economics, policy, and management areas, well beyond “nudges.” For example, behavioral experiments in health have investigated the effects of different co-payment rates and health insurance contracts on healthcare utilization and costs (Manning et al., 1987 ; Newhouse et al., 1981 ); the effects of public health insurance coverage on healthcare utilization and health outcomes (Baicker et al., 2013 ; Finkelstein et al., 2012 ; Finkelstein & Taubman, 2015 ; Finkelstein, Taubman, Allen, Wright, & Baicker, 2016 ); the effects of different providers’ incentives and the role of altruism (Ahlert et al., 2012 ; Brosig-Koch et al., 2016a , 2016b , 2017a , 2017b ; Fan, Chen, & Kann, 1998 ; Godager & Wiesen, 2013 ; Green, 2014 ; Hennig-Schmidt et al., 2011 ; Hennig-Schmidt & Wiesen, 2014 ; Kesternich et al., 2015 ; Kokot, Brosig-Koch, & Kairies-Schwarz, 2017 ); the role of audit, transparency, compliance, and gender bias in healthcare management (Godager, Hennig-Schmidt, & Iversen, 2016 ; Hennig-Schmidt et al., 2017 ; Jakobsson, Kotsadam, Syse, & Øien, 2016 ; Lindeboom, van der Klaauw, & Vriend, 2016 ); the role of different healthcare financing policies (Buckley, Cuff, Hurley, McLeod, Mestelman, & Cameron, 2012 ; Buckley, Cuff, Hurley, Mestelman, et al., 2015 , 2016 ); two-part tariffs for physician services (Greiner, Zhang, & Tang, 2017 ); provider competition (Bosig-Koch, Hehenkamp, & Kokot, 2017 ; Han, Kairies-Schwarz, & Vomhof, 2017 ); the matching markets for organ donations and for physicians and healthcare professionals (Herr & Normann, 2016 ; Kessler & Roth, 2012 , 2014a , 2014b ; Li, Hawley, & Schnier, 2013 ; Roth, 2002 ; Roth & Peranson, 1999 ); the role of subsidies for diagnostic tests and new health products (Cohen, Dupas, & Schaner, 2015 ; Duflo, Dupas, & Kremer, 2015 ; Dupas, 2014a , 2014b ; Dupas, Hoffman, Kremer, & Zwane, 2016 ); the choice of health insurance (Buckley, Cuff, Hurley, McLeod, Nuscheler, & Cameron, 2012 ; Huck et al., 2016 ; Kairies-Schwarz, Kokot, Vomhof, & Weßling, 2017 ; Kesternich, Heiss, McFadden, & Winter, 2013 ; Schram & Sonnemans, 2011 ); the economic and behavioral determinants of vaccination (Binder & Nuscheler, 2017 ; Böhm, Betsch, & Korn, 2016 ; Böhm, Meier, Korn, & Betsch, 2017 ; Bronchetti, Huffman, & Magenheim, 2015 ; Massin, Ventelou, Nebout, Verger, & Pulcini, 2015 ; Milkman, Beshears, Choi, Laibson, & Madrian, 2011 ; Tsutsui, Benzion, & Shahrabani, 2012 ); the effects of different types of HIV risk information and of SMS interventions on HIV treatment adherence (Dupas, 2011 ; Rana et al., 2015 ); the use of financial incentives for smoking cessation (Gine, Karlan, & Zinman, 2010 ; Halpern et al., 2015 ; 2016 ; Volpp et al., 2009 ), physical exercise (Charness & Gneezy, 2009 ; Royer, Stehr, & Sydnor, 2015 ), weight loss (John et al., 2011 ;John, Loewenstein, & Volpp, 2012 ; Kullgren et al., 2013 , 2016 ; Rao, Krall, & Loewenstein, 2011 ; Volpp et al., 2008 ), healthy eating (Loewenstein, Price, & Volpp, 2016 ), warfarin adherence (Kimmel et al., 2012 , 2016 ; Volpp et al., 2008 ), glucose control (Long, Jahnle, Richardson, Loewenstein, & Volpp, 2012 ), home-based health monitoring (Sen et al., 2014 ), mental exercises (Schofield, Loewenstein, Kopisc, & Volpp, 2015 ), immunization coverage (Banerjee, Duflo, Glennerster, & Kothari, 2010 ), nursing services (Banerjee, Duflo, & Glennerster, 2007 ), and medical drugs (Samper & Schwartz, 2013 ); the unintended carryover and spillover effects of financial incentives and nudges in health (Chiou, Yang, & Wan, 2011 ; Dolan et al., 2015 ; Dolan & Galizzi, 2014b , 2015 ; Müller et al., 2009 ; Wisdom, Downs, & Loewenstein, 2009 ); the behavioral effect of decision support systems and feedback (Cox et al., 2016 ; Eilermann et al., 2017 ); the elicitation of risk and time preferences in health and their links with health-related behaviors (Allison et al., 1998 ; Anderson & Mellor, 2008 ; Attema, 2012 ; Attema, Bleichrodt, & Wakker, 2012 ; Attema & Brouwer, 2010 , 2012 , 2014 ; Attema & Versteegh, 2013 ; Bleichrodt & Johannesson, 2001 ; Bradford, 2010 ; Bradford, Zoller, & Silvestri, 2010 ; Cairns, 1994 ; Cairns & van der Pol, 1997 ; Chapman, 1996 ; Chapman & Coups, 1999 ; Chapman & Elstein, 1995 ; Dolan & Gudex, 1995 ; Galizzi, Machado, & Miniaci, 2016 ; Galizzi & Miraldo, 2017 ; Galizzi, Miraldo, & Stavropoulou, 2016 ; Galizzi, Miraldo, Stavropoulou, & van der Pol, 2016 ; Garcia Prado, Arrieta, Gonzalez, & Pinto-Prades, 2017 ; Harrison et al., 2015 ; Harrison, Lau, & Rutström, 2010 ; Michel-Lepage, Ventelou, Nebout, Verger, & Pulcini, 2013 ; Sutter et al., 2013 ; Szrek, Chao, Ramlagan, & Peltzer, 2012 ; van der Pol & Cairns, 1999 , 2001 , 2002 , 2008 , 2011 ), the elicitation of preferences for retransplantation (Ubel & Loewenstein, 1995 ), and end-of-life decisions (Halpern et al., 2013 ).
Nudges are just one of the many areas of applications. They tend to be relatively effective in the health contexts where people suffer from “internalities,” costs that we incur because we fail to account for our future selves (Herrnstein, Loewenstein, Prelec, & Vaughan, 1993 ). Many other health situations are, however, also affected by externalities. Other policy tools, such as taxes, subsidies, and regulatory interventions, have been documented to deal effectively with externalities in health markets (Bhargava & Loewenstein, 2015 ; Galizzi, 2017 ). The application of behavioral experiments to these policy areas is at the moment almost nonexistent, and we foresee an increase of applications in this key area.
Another related aspect for both research and policy purposes is the rationale informing the legitimacy of nudging people. There is a major gap in the literature in measuring underlying preferences before the nudging interventions take place, and in monitoring their evolution (if any) before and after being nudged. This would help in understanding heterogeneity in behavioral change, as well as in identifying the behavioral channels, mechanisms, and mediating factors that are activated when individuals’ behavior is nudged. At the same time, it would inform the design of target-specific nudges, incentives, and behavioral regulatory tools (thus advancing the state-of-the-art evidence beyond knowing just “what works”). The issue of which set of preferences should be considered for drawing a welfare analysis of nudges and other behavioral interventions is one of the most relevant and pressing open questions from both a conceptual and an empirical perspective, as well as another area of promising development for the next waves of behavioral experiments in health.
While a neutral framing of the experimental decision is appropriate in an experiment on decision-making in games of strategic interactions, a medical framing appears natural for behavioral experiments on decision-making in medical contexts. Kesternich et al. ( 2015 ) show that framing in a health context affects subjects’ behavior in modified dictator and trilateral distribution games. In particular, in their health frame, subjects decide on the role of physicians in the provision of medical services with consequences for real patients outside the lab (similar to Hennig-Schmidt et al., 2011 ) in the modified dictator game. In a trilateral distribution game, consequences for the insured bearing the cost of medical service provision are also added.
More generally, recent practice in behavioral experiments in health is aligned with the belief that unless you frame a decision situation—for example in a medical or health frame—a researcher cannot be sure how subjects in an experiment have perceived the decision situation (Galizzi & Navarro-Martinez, 2019 ; Harrison & List, 2008 ). It may thus be crucial in chosen effort tasks to set subjects in the context the experimenter wants to study in order to avoid the possibility that subjects may impose a context on the abstract experimental task that is different from the experimenter’s intended context (e.g., Engel & Rand, 2014 ; Harrison & List, 2004 ). As Harrison and List ( 2004 ) notice, “it is not the case that abstract, context-free experiments provide more general findings if the context itself is relevant to the performance of the subjects” (p. 1022).
It remains unclear, however, whether a change in behavior due to framing more or less accurately reflects true behavior of healthcare professionals. One may argue that a healthcare professional in a health-framed study may be more willing to forgo earnings to avoid looking bad (“experimenter demand effect”; Zizzo, 2010 ). In practice, healthcare professionals in a neutrally framed decision situation could even become less responsive to how choices directly affect patients than when facing a series of choices in a framed task. Further, individuals may value their health and the health of others differently than any other good. Therefore, both unframed and framed experiments may misinterpret choices by healthcare professionals. For these reasons, it is important to study whether a medical framing in experiments more accurately reflects behavior in healthcare delivery (Cox, Green, & Hennig-Schmidt, 2016 ; Kesternich, Schumacher, & Winter, 2015 ).
Further, different subject pools used in health-related experiments (nonmedical students, medical students, physicians) may significantly change behavioral results, with nonmedical students exerting less patient-regarding altruism (Brosig-Koch et al., 2017a ; Hennig-Schmidt & Wiesen, 2014 ). Considering fraudulent behavior in a routine task in neonatal intensive care units (entry of weights in the birth reports), Hennig-Schmidt et al. ( 2017 ) found some evidence for more honest behavior of medical students compared to economics students. A few studies with healthcare professionals and medical students in developing countries correlate neutrally framed social preferences with actual health-related behaviors (e.g., Brock, Lange, & Leonard, 2016 ; Kolstad & Lindkvist, 2012 ).
Taken together, three promising avenues for behavioral experiments in health on this issue are (i) rigorously and systematically testing the behavioral effects of framing and subject pools; (ii) extending initial findings from the laboratory to field experiments, ideally with healthcare professionals (Cox, Sadiraj, Schnier, & Sweeney, 2016 ; Eilermann et al., 2017 ; Leeds et al., 2017 ); and (iii) linking findings from behavioral experiments to actual health-related behaviors. In this sense, it seems thus appropriate to call, again, for more systematic evidence—also from healthcare systems in developed countries—to be able to gather more conclusive predictions of providers’ behavior in the field.
The specificity of health as a policy domain is self-evident. On the one hand, health is a very special area of policy application for obvious ethical and political reasons, and even more so for the application of randomized controlled behavioral experiments. Health, moreover, is a research and policy area that is uniquely rich in data: think about the millions of yearly entries in healthcare records and administrative registers (e.g., the Hospital Episode Statistics in the United Kingdom); the large epidemiological cohorts and clinical RCTs; and the complex databanks containing the genetic and epigenetic profiling at a population level. It is also unclear from both a conceptual and an empirical point of view whether behaviors and decisions in the health domain merely reflect behaviors and decisions in other domains in life, for example in the financial domain. As mentioned, the small experimental literature on cross-domain preferences seems to suggest that preferences are not stable across the health and monetary domains. Also the literature on the use of financial incentives in health finds that their effects are less straightforward and universally applicable than in other fields of applications (Gneezy, Meier, & Rey-Biel, 2011 ). A more specific example is healthcare provider incentives. Recent experimental findings suggest that healthcare providers’ behavior seems to be affected by pay-for-performance pay, but that this might also lead to adverse effects, such as motivation crowding-out (e.g., Brosig-Koch et al., 2016a , 2017b ; Oxholm, 2016 ). The latter pattern is, for example, not observed in other working domains (admittedly with different performance schemes), such as in field experiments with teachers (e.g., Muralidharan & Sundararaman, 2011 ). Therefore, a note of caution is in order when extrapolating lessons from experiments in other fields and generalizing them to the health domain.
On the other hand, behavioral health economists should be careful in advocating a complete disconnection of health applications from other areas of application of behavioral and experimental economics. On the contrary, they should continue arguing that there is much that can be learned from health applications that is useful to other policy domains. This can also help to reduce the substantial disengagement between economic and medical journals. For example, generalist economic journals seem to regularly publish behavioral experiments in, for example, education, financial savings, and energy consumption more regularly than in health, which are sometimes dismissed as “too field-specific.” That health is of more, not less, general interest than other subfields of economics is directly confirmed by the stellar impact factor and international reputation and visibility of the medical journals.
It is true that, at the moment, there is very little evidence on the long-term carryover effects and on the cross-behavioral spillover effects of nudges, incentives, and other health policy interventions (Dolan & Galizzi, 2014a , 2015 ; Dolan et al., 2015 ). This is also due to the fact that, in practice, it is difficult to design behavioral experiments that follow up subjects over time for periods of time longer than a couple of hours (in the lab) or a few weeks or months (in the field), or that track all the complex ramifications of an initial policy intervention on the whole set of targeted and nontargeted health behaviors.
There is, more generally, a sort of major gap and disconnection between two key sources of empirical evidence in health economics. On the one hand, the behavioral experiments in health are typically conducted with small samples of subjects and almost invariably are centered on a single observation window or a single data collection point. On the other hand, very comprehensive longitudinal data sets exist in health in forms of administrative records for healthcare access (e.g., the Hospital Episode Statistics in the United Kingdom), biomarkers banks (e.g., the UK Biobank in the United Kingdom), or medical records and biomarkers for epidemiological cohorts (e.g., Constances in France).
The time seems ripe to systematically link and integrate these two major data sources. The already mentioned recent spring of experiments on “behavioral data linking” has shown that it is indeed feasible to link and merge behavioral economics experiments with other data sources, such as longitudinal surveys, online panels, administrative records, biomarkers and epigenetics banks, apps and mobile devices, smart cards and scan data, clinical RCTs, and other big data sources (Andersen et al., 2015 ; Galizzi, Harrison, & Miniaci, 2017 ). Given the inherent data-richness of health as a research and policy domain, we expect behavioral data linking to become a key building block of the next generation of behavioral experiments in health. This will contribute to further integrating and cross-fertilizing insights, tools, and methods from behavioral, experimental, and health economics, and to shaping up a groundbreaking interdisciplinary area at the interface between behavioral, medical, and data sciences.
This article reviews the state of the art of behavioral experiments in health by critically discussing ten key areas of potential debate and misconception, by highlighting their theoretical and empirical rationale and scope, and by discussing the significant questions which remain.
As our discussions indicate, there are many areas within health economics where experimental methods can be applied fruitfully. To date, in fact, a broad spectrum of behavioral experiments from the lab to the field have already been applied to numerous different health-related areas, including, for example, the effects of different co-payment rates and health insurance contracts on healthcare utilization and costs; the effects of public health insurance coverage on healthcare utilization and health outcomes; the effects of different providers’ incentives and the role of altruism; the role of audit, transparency, compliance, and gender bias in healthcare management; the role of different healthcare financing policies; the matching markets for organ donations and for physicians and healthcare professionals; the role of subsidies for diagnostic tests and new health products; the choice of health insurance; the economic and behavioral determinants of vaccination; the effects of different types of HIV risk information and of SMS interventions on HIV treatment adherence; the use of financial incentives and nudges for smoking cessation, physical exercise, weight loss, healthy eating, warfarin adherence, glucose control, home-based health monitoring, mental exercises, immunization coverage, and medical drugs; the unintended carryover and spillover effects of financial incentives and nudges in health; the behavioral effect of decision support systems and feedback; the elicitation of risk and time preferences in health and their links with health-related behaviors; and the elicitation of preferences for retransplantation and end-of-life decisions. Many other health-related areas are expected to follow in the next years in both developing and developed countries.
Tailoring and fine-tuning the broad spectrum of lab, field, online, mobile, and “behavioral data linking” experiments in order to address pressing health policy challenges and key research questions is, both methodologically and substantially, one of the most promising and exciting areas of applications of behavioral experiments to health economics. Also, via the new international networks, the next cohort of behavioral experiments in health is likely to originate from a closer collaboration among behavioral and experimental economists, health economists, medical doctors, and decision makers in health policy and management. This forthcoming generation of behavioral experiments in health will likely scale up the current endeavors to systematically link behavioral economics measures to other data sources, in which health is naturally rich. In the years to come, the promise and the research and policy impact of behavioral experiments in health are only destined to grow.
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Individual games, computerised games and experiments.
Many students respond well to being involved in a game and the experience can fix a concept vividly in their minds. We have guides and, in some cases, printable materials to help you introduce games to your classes.
Economic Classroom Experiments is a chapter of the Handbook for Economics Lecturers with advice and examples.
Simulations, Games and Role-Play is an older Handbook chapter, discussing why, when and how to use games or simulations in teaching economics, with examples.
Classroom Experiments, Games and Role-Play a series of experiments and games from our Reflections on Teaching section.
IREE Volume 9 Issue 2 was a special issue on economic classroom experiments, including review papers as well as details of individual experiments.
Using Experiments and Activities in the Principles Class by John Eaton describes a number of games, used analogously to lab sessions for physical science students
John Sloman summarises seven games that can be used to increase student motivation (Powerpoint, with links to handouts and other materials)
Jon Guest describes using classroom experiments as a more active method of teaching microeconomics in a first-year context and an intermediate context .
The FEELE team have created an extensive guide to Economic Classroom Experiments , including The Twenty Pound Auction . It's part of Wikiversity, so you can log in to add your own experiences and variations.
Games Economists Play: Non-Computerized Classroom-Games for College Economics is an online guide to 180 games both for micro principles and macro principles (external link).
Health Economics education (HEe) lists several classroom experiments for teaching Health Economics .
The International Trade Game: Using just scissors, pencils, rulers and paper, large numbers of students experience a simulation of international trade.
The Tennis Balls Game: students form a "production line" to illustrate diminishing marginal returns. This is one of a number of games used by Mary Hedges and colleagues , including the oligopoly game (favourite TV show) , Money Supply Game and the Restaurant Game (an auction market).
A separate page discusses some games that can be used with school students, for example on open days. These include the public goods game and rent-seeking game (both using playing cards), auctioning a £1 coin (illustrating sunk cost and marginal cost) and a public goods game with altruistic punishment .
Charles Holt's VEconLab is a set of 35 interactive games that can be configured by lecturers and played by students using only their web browsers. Each game has extensive instructions.
Econport is another site allowing you to run a variety of experiments using the web. They provide extensive documentation on how to integrate the experiments into courses.
Finance and Economics Experimental Laboratory at Exeter (FEELE) , at Exeter University, has created 13 online games. You can register for free to create, customise and run economic experiments online. Jon Guest's case study describes using one of these experiments in a class.
Economics-games.com is another site along similar lines. It has 14 simulations for students to play on their own, and 48 multiplayer games that lecturers can configure and share via a web link. The site is free and students can play from computers, phones or other internet devices.
LIONESS is a free web-based platform for interactive online experiments, developed at the University of Nottingham and University of Passau. The control panel lets experimenters design and conduct experiments. Participants take part via personalised links.
oTree is a framework for coding multi-player experiments and games, based on the Python language. Experiments can be created by writing code and/or assembling components in a point-and-click interface. They can be run on the Web or downloaded. There is a long list of experiments and games created by the community .
ClassEx , based at the University of Passau, is a widely-used platform for online surveys and classroom experiments. Students make their decisions via their computers or mobile devices, and the outcomes appear on the lecturer's computer for them to present to the group. The CORE Project have released a video of a lecture by Cloda Jenkins (UCL) in which Prof Jenkins incorporates three ClassEx games.
Ariel Rubinstein's site, Didactic Web-Based Experiments in Game Theory , has free online games and suggestions for using them in class. "After having registered, a teacher, will be able to allocate problems to the students and get basic statistics on their responses. [...] My goal as a teacher is to deliver a loud and clear message that game theoretic models are not meant to supply predictions of strategic behavior in real life."
MobLab is a classroom gaming and polling system that takes a paid subscription per student per class. Its dozens of games can be browsed by course and can be configured by the lecturer. Its grade book can sync to VLE software.
The Teach Better podcast has an episode from July 2017 in which Matt Olczak of Aston Business School discusses using economics-games.com and VEconLab, and Bob Gazzale of the University of Toronto discusses his use of MobLab. Matt Olczak also wrote a blog post for Inomics Teach introducing some online games .
zTree , the Zurich Toolbox for Readymade Economic Experiments, is a client/server software package that runs locally on Windows computers (including virtual machines), rather than over the Web.
Kiviq is a dedicated educational tool for running double auctions in a classroom setting.
For a stock market game , see HowTheMarketWorks.com .
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Scientific Reports volume 14 , Article number: 20317 ( 2024 ) Cite this article
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Carbon emission reduction is crucial for mitigating global climate change, and green fiscal policies, through providing economic incentives and reallocating resources, are key means to achieve carbon reduction targets. This paper uses data covering 248 cities from 2003 to 2019 and applies a multi-period difference-in-differences model (DID) to thoroughly assess the impact of energy conservation and emission reduction ( ECER ) fiscal policies on enhancing carbon emission ( CE 1 ) reduction and carbon efficiency ( CE 2 ). It further analyzes the mediating role of Green Innovation ( GI ), exploring how it strengthens the impact of ECER policies. We find that: (1) ECER policies significantly promote the improvement of carbon reduction and CE 2 , a conclusion that remains robust after excluding the impacts of concurrent policy influences, sample selection biases, outliers, and other random factors. (2) ECER policies enhance CE 1 reduction and CE 2 in pilot cities by promoting green innovation, and this conclusion is confirmed by Sobel Z tests. (3) The effects of ECER policies on CE 1 reduction and the improvement of CE 2 are more pronounced in higher-level cities, the eastern regions and non-resource cities. This research provides policy makers with suggestions, highlighting that incentivizing green innovation through green fiscal policies is an effective path to achieving carbon reduction goals.
Introduction.
Efforts to mitigate global climate change through the reduction of CE 1 have emerged as a shared objective among nations globally 1 . From the initiation of the United Nations Framework Convention on Climate Change to the enactment of the Kyoto Protocol and the adoption of the Paris Agreement, these pacts reflect the unified resolve of nations to tackle global climate change 2 , 3 . With the acceleration of global industrialization and the continuous increase in energy demand, there has been a significant rise in the emissions of greenhouse gases, especially carbon dioxide, posing an unprecedented challenge to the Earth’s climate system 4 . These issues encompass the escalation of average global temperatures, a surge in severe weather occurrences, accelerated glacier melt, and a persistent increase in sea levels 5 , 6 , 7 , which threaten the balance of natural ecosystems and have profound impacts on the economic development and well-being of human societies. Therefore, adopting effective carbon reduction strategies to slow these climate change trends has become an urgent task faced globally.
In the current field of CE 1 reduction research, the focus is mainly on implementing policies such as carbon emission trading 8 , smart city pilot policies 9 , and low-carbon city pilot policies 10 . Among these policies, green fiscal policy, as a core strategy to mitigate the impact of climate change, is increasingly recognized by the academic community and policymakers for its importance in promoting CE 1 reduction 11 , 12 . This policy directly impacts CE 1 in economic activities through adjustments in the tax system, provision of fiscal subsidies, and increased investments in renewable energy and low-carbon technologies 13 . Green fiscal policies differ from traditional environmental protection measures by employing a mechanism that combines incentives and constraints, aiming to encourage enterprises to adopt emission reduction measures. In the implementation process of green fiscal policies, governments encourage enterprises to reduce CE 1 by adjusting tax policies 14 . Specifically, the ECER policy impacts the carbon emissions of demonstration cities through a combination of financial incentives and target constraints. The demonstration period lasts for three years, during which the central government provides reward funds for demonstration projects. The amount of these rewards is determined by the category of the city: 600 million RMB annually for municipalities and city clusters, 500 million RMB annually for sub-provincial cities and provincial capitals, and 400 million RMB annually for other cities. Local governments have the discretion to decide how to utilize these funds, while the central government is responsible solely for project record management. Additionally, the central government conducts annual and overall target assessments of the demonstration cities. The results of the annual assessment influence the reward funds for the following year: cities that perform excellently will receive an additional 20% of reward funds, while those that fail to meet the standards will have 20% of their funds withdrawn. The overall assessment results are linked to the demonstration qualification and reward funds; cities that fail to meet the overall targets or have serious issues will lose their demonstration status and have all reward funds withdrawn. This financial incentive mechanism ensures that local governments have sufficient financial support when implementing green technologies and projects, promoting increased energy efficiency and the widespread adoption of clean energy. Simultaneously, through the target constraint mechanism, the central government strictly supervises and incentivizes local governments’ efforts to reduce emissions, ensuring effective policy implementation. Under the dual pressure of financial incentives and performance assessments, local governments actively adopt various measures to promote energy conservation and emission reduction, including investing in green infrastructure, promoting energy-saving technologies, and optimizing energy structures, thereby achieving significant reductions in carbon emissions.
Furthermore, innovation and technological breakthroughs significantly enhance the effectiveness of green fiscal policies in reducing carbon emissions. Specifically, technological advancements improve energy efficiency, reducing the energy consumption per unit of output; they lower the production costs of clean energy, promoting its widespread adoption; and they advance carbon capture and storage technologies, directly reducing industrial carbon dioxide emissions. These technological improvements bolster the impact of green fiscal policies, making them more effective in achieving carbon reduction targets. However, the implementation of green fiscal policies also faces some challenges. Firstly, balancing the relationship between economic development and environmental protection to avoid potential negative impacts such as job losses and industrial relocation during policy execution is an issue that policymakers need to consider. Secondly, the effective implementation of green fiscal policies requires strong policy support and regulatory mechanisms to ensure that policy measures are effectively executed and can adapt to constantly changing economic and environmental conditions. Therefore, evaluating the carbon reduction effect of such policies is of significant importance for achieving long-term environmental sustainability and promoting the green economic transformation.
This paper analyzes the impact of green fiscal policies on carbon emissions and carbon efficiency. Relevant research mainly focuses on the following two areas: studies on the factors influencing carbon emissions, and research related to environmental regulations and energy conservation and emission reduction fiscal policies.
Firstly, a substantial body of literature focuses on the factors influencing carbon emissions, with some studies specifically examining the impact of government intervention and environmental regulation on CO2 emissions. These studies are closely related to the theme of this paper. From an economic perspective, numerous studies have demonstrated that economic growth significantly impacts carbon emissions 15 , 16 , 17 . Generally, increased economic activity is associated with higher energy consumption, leading to higher carbon emissions. However, as economies reach a certain level of development, the Environmental Kuznets Curve (EKC) phenomenon may occur, where carbon emissions begin to decrease after reaching a certain economic threshold 18 , 19 . Research has also confirmed that economic growth increases the ecological footprint, leading to environmental degradation 20 . For example, economic growth, income inequality, and energy poverty have increased environmental pressure in BRICS countries 21 . In Pakistan, institutional quality has led to higher CO 2 emissions, but economic development can help reduce these emissions 22 . From a social perspective, the acceleration of urbanization is typically accompanied by increased energy consumption, thereby raising carbon emissions. There is a long-term and short-term U-shaped relationship between urbanization and the environment 23 . Upgrading existing infrastructure can enable various sectors to produce minimal waste that impacts emissions 24 . Changes in consumption levels and population structure also significantly affect carbon emissions 25 . From a policy perspective, government-enacted environmental regulations and policies, such as carbon taxes, carbon trading markets, emission standards, and renewable energy subsidies, play a crucial role in reducing carbon emissions. Innovations and environmental policies contribute to emission reductions both in the long and short term. Additionally, carbon pricing can reduce emissions in specific regions, although its impact is often more targeted at specific countries 26 . Carbon taxes and mitigation technologies are helping to achieve sustainable development goals for carbon mitigation 27 . Green energy investments are significantly associated with greenhouse gas emissions and support environmental quality 28 . However, these studies often overlook the impact of energy conservation and emission reduction fiscal policies on carbon emissions.
Secondly, there is a body of literature focusing on environmental regulation, which can be divided into two main areas: the impact of environmental regulation on the environment and its impact on the economy. On the one hand, extensive research has explored the environmental impact of regulation. Studies generally agree that stringent environmental regulations help reduce pollutant emissions and improve environmental quality. Environmental regulations significantly enhance the synergy between carbon reduction and air pollution control 29 . Target-based pollutant reduction policies effectively constrain the sulfur dioxide emissions of regulated enterprises, lowering their sulfur dioxide emission intensity, thereby demonstrating that stringent environmental regulations facilitate green transitions for businesses 30 . However, in some developing countries or regions with weak enforcement, the effectiveness of environmental regulations may be compromised. Despite strict regulatory policies being in place, inadequate enforcement or a lack of regulatory capacity may result in actual pollutant reduction falling short of expectations. On the other hand, part of the literature examines the economic impact of environmental regulation. Some studies suggest that environmental regulation can drive technological innovation and industrial upgrading, thereby promoting economic growth 31 . Strict environmental standards force companies to improve production processes and develop new environmental technologies, which can create new economic opportunities and growth points 32 . Environmental regulations significantly enhance green technological innovation 33 , and they have notably promoted green innovation across European countries 34 . Conversely, environmental regulations may increase operational costs for businesses, particularly in the short term due to compliance costs, which could inhibit economic growth. This is especially true for regions or countries that rely heavily on high-pollution, high-energy-consumption industries, where environmental regulation might lead to a slowdown in economic growth. Given that energy conservation and emission reduction fiscal policies are a form of environmental regulation, it is necessary to evaluate their effectiveness.
Thirdly, some literature evaluates the governance effectiveness of energy conservation and emission reduction fiscal policies. From an environmental perspective, these policies can reduce pollutants and enhance efficiency. On average, such policies have reduced industrial SO2 (sulfur dioxide) emissions by 23.8% and industrial wastewater discharge by 17.5% 35 . Additionally, energy conservation and emission reduction fiscal policies can effectively improve green total factor carbon efficiency 36 . From an economic perspective, these policies can promote investment and economic growth 37 . They have significantly improved green credit for enterprises and can facilitate sustainable urban development 38 .
In summary, there are two significant gaps in the existing literature. Firstly, although numerous studies have extensively explored the factors influencing carbon emissions from economic, social, and policy perspectives, relatively few have examined the relationship between ECER policies and carbon emissions. Specifically, most of the existing literature focuses on the impact of macroeconomic policies, industrial structure adjustments, and technological innovation on carbon emissions. However, there is a lack of systematic empirical analysis on how specific fiscal incentives directly affect carbon emissions, limiting our comprehensive understanding of the actual effects of fiscal policies on emission reduction. Secondly, most of the existing studies investigate carbon dioxide emissions from a single perspective, such as focusing on total carbon emissions, carbon intensity, or carbon efficiency. These studies lack a multi-faceted exploration of the relationship between a single policy and carbon emissions. Typically, research adopts a specific metric to measure policy effects, but this approach overlooks how different metrics might reveal various aspects of policy impact. Consequently, these studies fail to capture the multi-dimensional effects of policies on reducing carbon emissions comprehensively. This single-perspective research methodology cannot adequately reflect the multiple impacts of policies on carbon emissions across different scenarios and time periods. This paper aims to evaluate the impact of the ECER policy, jointly introduced by the Ministry of Finance and the National Development and Reform Commission in 2011, on CE1 and CE2. Given that the ECER policy was implemented in three batches of pilot cities, this study employs a multi-period Difference-in-Differences (DID) model for analysis. The advantage of this model lies in its ability to compare the effects of the policy before and after its implementation across multiple time points, thereby capturing the dynamic impacts of the policy. Furthermore, this article explores the mediating role of green innovation in the impact process of the ECER policy, revealing the policy’s varying effects on CE 1 and CE2 across different regions through heterogeneity analysis.The marginal contributions of this article: Firstly, this paper evaluates the relationship between ECER policies and carbon emissions, addressing a significant gap in the existing research. Although numerous studies have explored various factors influencing carbon emissions from different perspectives, there is a lack of systematic research on the actual effects of specific fiscal policies on energy conservation and emission reduction, particularly their direct impact on carbon emissions. Through empirical analysis and data validation, this study thoroughly investigates the specific mechanisms and effects of ECER policies on carbon emissions in practice, thus filling this research gap. Secondly, this paper systematically assesses the relationship between ECER policies and carbon emissions from two key perspectives: total carbon emissions and carbon efficiency. By considering these two important indicators, this study not only examines the impact of ECER fiscal policies on overall carbon emissions but also analyzes their role in improving carbon efficiency. Through an in-depth analysis of these two metrics, this paper provides a more comprehensive and multi-dimensional view, systematically evaluating the effectiveness and mechanisms of ECER policies.
The remainder of the article is organized as follows: the second part discusses the policy background and theoretical analysis; the third part details the model settings and variable explanations; the fourth part presents the empirical analysis; the fifth part analyzes regional heterogeneity; and the last part concludes with conclusions and policy recommendations.
Policy background.
In 2011, the Ministry of Finance and the National Development and Reform Commission issued the “Notice on Conducting Comprehensive Demonstration Work of Fiscal Policies for Energy Conservation and Emission Reduction,” deciding to carry out comprehensive demonstrations of fiscal policies for ECER in some cities during the “Twelfth Five-Year” period. Beijing, Shenzhen, Chongqing, Hangzhou, Changsha, Guiyang, Jilin, and Xinyu were selected as the first batch of demonstration cities. In the subsequent years of 2013 and 2014, 10 and 12 cities were respectively chosen as pilot cities for the fiscal policies on ECER . Specifically, this policy uses cities as platforms and integrates fiscal policies as a means to comprehensively carry out urban ECER demonstrations in various aspects, including industrial decarbonization, transportation clean-up, building greening, service intensification, major pollutant reduction, and large-scale utilization of renewable energy. Its main goal in terms of CE 1 reduction is to establish a concept of green, circular, and low-carbon development in the demonstration cities, achieve widespread promotion of low-carbon technologies in industries, construction, transportation, and other fields, lead the pilot cities in ECER efforts across society, and significantly enhance their capacity for sustainable development. Figure 1 presents the spatial distribution of ECER policy pilot cities in the years 2011, 2013, and 2014 (This figure was created using ArcMap software).
Distribution of ECER Policy Pilot Areas (Plan Approval Number GS(2019)1822).
Carbon emission reduction effect of green fiscal policy.
Green fiscal policy, as a significant environmental governance tool, promotes the transformation of the economic and social system towards low-carbon, sustainable development through fiscal measures 39 . Its CE 1 reduction effects can be described from the following aspects. Firstly, green fiscal policy encourages the research and application of green technologies through economic incentives (such as tax reductions and fiscal subsidies) 40 . These technologies include energy efficiency improvement technologies, clean energy technologies, and carbon capture and storage technologies, which directly reduce energy consumption and CE 1 in economic activities. Secondly, green fiscal policy influences the behavior of consumers and producers by affecting the price mechanism. The imposition of a carbon tax raises the cost of CE 1 , reflecting the external cost of CE 1 on the environment, encouraging enterprises to take emission reduction measures, and prompting consumers to prefer low-carbon products and services 41 . The change in price signals promotes the transformation of the entire society’s energy consumption structure towards more efficient and low-carbon directions. Furthermore, green fiscal policy can support CE 1 reduction-related infrastructure construction and public service improvements through the guidance and redistribution of funds. This includes the construction and optimization of public transportation systems, urban greening, and forest conservation projects, which not only directly or indirectly reduce CE 1 but also enhance the carbon absorption capacity of cities and regions. Lastly, green fiscal policies, by raising public environmental awareness and participation, create a conducive atmosphere for all sectors of society to join in carbon reduction efforts 42 . Governments can increase public awareness of climate change and inspire a low-carbon lifestyle through the promotion and education of fiscal policies, providing broader social support for carbon reduction 43 .
Green fiscal policies not only drive a reduction in CE 1 but also stimulate sustainable economic growth. By taxing high-carbon activities, offering financial subsidies and incentives for green projects, these policies channel capital towards low-carbon and green industries. This not only mitigates negative environmental impacts but also fosters the development of emerging green technologies and sectors. As the green industry expands and low-carbon technologies become more widespread, economic growth increasingly relies on clean and efficient energy use 44 , thereby enhancing the CE 2 . Thus, the implementation of green fiscal policies demonstrates a commitment to transitioning towards a low-carbon economy, playing a crucial role in the global response to climate change, achieving a win–win for environmental protection and economic growth.
Based on this, the article proposes hypothesis 1: Green fiscal policies can promote CE 1 reduction effects and enhance CE 2 .
Green innovation is a key factor in driving sustainable development, particularly playing a significant role in CE 1 reduction and efficiency enhancement. By introducing and adopting new environmentally friendly technologies and processes, green innovation not only significantly reduces greenhouse gas emissions but also enhances the efficiency of energy use and resource management, thus promoting a harmonious coexistence between economic activity and environmental protection. Green innovation, through the development and adoption of renewable energy technologies such as solar, wind, and biomass energy, directly reduces reliance on fossil fuels and the corresponding CE 1 . The application of these technologies not only reduces the carbon footprint but also promotes the diversification of energy supply and enhances energy security 45 . Green innovation also plays an essential role in improving energy efficiency. By adopting more efficient production processes and energy-using equipment, businesses and households can accomplish the same tasks or meet the same living needs with lower energy consumption, thus reducing CE 1 46 . Additionally, green innovation encompasses the concepts and practices of the circular economy, which encourages the reuse, recycling, and recovery of materials, reducing the extraction and processing of new materials and further lowering CE1s in the production process 47 . Green innovation includes the development of Carbon Capture, Utilization, and Storage (CCUS) technologies, which can directly capture carbon dioxide from industrial emissions and either convert it into useful products or safely store it, thereby reducing the carbon content in the atmosphere 48 . On the policy and management level, green innovation also involves establishing and refining mechanisms such as carbon pricing, green taxes, and carbon trading, which promote the adoption of low-carbon and environmentally friendly technologies and behaviors among businesses and individuals through economic incentives 49 . Based on this, the article proposes hypothesis H2: Green fiscal policies can promote CE 1 reduction effects and CE 2 by fostering green innovation.
In conclusion, the theoretical framework, as shown in Fig. 2 .
Theoretical framework.
To address the limitations faced by traditional regression models in evaluating policy implementation effects, this study utilizes DID model for analysis. Given the variation in the policy implementation years in this paper, the traditional DID model cannot be used 50 . Accordingly, this paper draws on the approach of Beck et al. 51 , employing a DID with multiple time periods to assess the policy effects, with the model set up as follows:
Y in the model is the explained variable, indicating CE 1 and CE 2 of the city i in the annual t . Treated i is the group variable, where it takes the value 1 if city i belongs to the treatment group, and 0 if it belongs to the control group; Post it is the post-treatment period dummy variable, where it takes the value 1 for city i in year t if ECER policy has been officially implemented, and 0 if it has not been officially implemented. This study investigates the impact of energy conservation and emission reduction fiscal policies on urban CE 1 and CE 2 by examining the effect of the interaction term Treated × Post it on the dependent variable. The coefficient β 1 measures the impact of the policy on the dependent variable. Controls in this study represent control variables, specifically urbanization rate ( lnur ), foreign direct investment level ( lnfdi ), industrial structure ( lnis ), level of scientific and technological expenditure ( lnsst ), and fiscal revenue and expenditure level ( lnfre ), among others. \(\nu\) , \(\tau\) and \(\varepsilon\) represent city fixed effects, time fixed effects, and random error terms, respectively.
Considering the three-year implementation period of green fiscal policies, it is necessary to establish an exit mechanism for the treatment group. Drawing on existing literature 12 , this paper constructs the following treatment groups: the first batch of pilot cities from 2011 to 2014 is set to 1; the second batch of pilot cities from 2013 to 2016 is set to 1; the third batch of pilot cities from 2014 to 2017 is set to 1, with other years set to 0. The pilot cities are shown in Fig. 3 .
ECER policy implementation period.
Explained variables.
Carbon Emissions: Drawing from existing literature, this article utilizes current CE 1 data to calculate CE 1 52 , 53 . It follows the guidelines on greenhouse gas emission allocations by the IPCC , taking into account the emissions of carbon dioxide within the administrative boundaries of each city. Territorial emissions refer to emissions occurring within the managed territory and maritime areas under the jurisdiction of a region 54 , including emissions from socio-economic sectors and direct residential activities within regional boundaries 55 .
Carbon Efficiency: Following existing literature, this paper measures CE 2 using the ratio of CE 1 to GDP 56 .
In examining the correlation between CE 1 and economic efficiency, Fig. 4 a provides an overview of the evolution of CE 1 from 2003 to 2019, while Fig. 4 b offers a detailed portrayal of the progress in CE 2 over the same period. Figure 4 a reveals a steady increase in total CE 1 beginning in 2002, with a notable acceleration post-2009, peaking in 2017. Despite some fluctuations and a slight dip in 2018, the figures for 2019 remained just below the peak, overall indicating an upward trajectory. In contrast, Fig. 4 b demonstrates a year-on-year improvement in CE 2 , measured in tens of thousands of yuan output per ton of carbon emitted, starting in 2003. The pace of growth accelerated significantly after 2011, reaching its zenith in 2019. This signifies a substantial rise in the economic output efficiency per unit of carbon emitted, revealing a reduction in carbon dependency within economic activities. The combined analysis of both figures indicates that, alongside economic growth, there has been a notable advancement in optimizing CE 2 .
Trends in CE 1 ( a ) and CE 2 ( b ) (2003–2019).
To eliminate the interference of omitted variables on the research results, this article selects the following control variables 57 , 58 : Urbanization rate ( lnur ), which refers to the ratio of urban population to total population; Level of foreign direct investment ( lnfdi ), the ratio of actual foreign investment to the GDP ; Industrial structure ( lnis ), the proportion of the secondary industry in GDP ; Level of science and technology expenditure ( lnsst ), the ratio of science and technology expenditure in ten thousand to GDP in hundred billion; Fiscal revenue and expenditure level ( lnfre ), the sum of local fiscal budget revenue and expenditure to GDP . To reduce heteroscedasticity in the data, this article takes the logarithm of all control variables. Table 1 reports the definitions of the main variables in this paper.
We selects cities at the prefecture level in China from 2003 to 2019 as the research sample. Considering that missing data can affect the results, this paper excludes samples with missing data, ultimately obtaining 3134 samples. The CE 1 data in this paper comes from the China Emissions Accounts and Datasets (CEADs), which provides CE 1 data from 1997 to 2019, so the sample period for this paper ends in 2019. The control variable data are all sourced from the China City Statistical Yearbook covering the years 2004 to 2020. Table 2 provides descriptive statistics for the main variables in this paper.
In a quasi-natural experiment, various factors may influence the relationship between the implementation of green fiscal policies and the reduction of carbon emissions. To address this, we employed multiple methods to control for these potential confounding variables. Firstly, we introduced control variables to eliminate or reduce the interference of external factors on the main research relationship, ensuring the accurate estimation of the effects of green fiscal policies. Secondly, we adopted a two-way fixed effects model to control for time-invariant city characteristics and potential common time trends. Thirdly, we conducted parallel trend tests to verify whether the trends of the treatment and control groups were consistent before the policy implementation, ensuring the validity of the Difference-in-Differences (DID) estimates. Additionally, we performed multiple robustness checks, including propensity score matching and excluding the effects of other concurrent policies, to test the robustness of the results. Finally, we confirmed the reliability of the results through placebo tests. These methods collectively help to effectively reduce the interference of external variables, ensuring the accuracy and reliability of the research findings.
Benchmark regression analysis.
We employs a two-way fixed effects model for the empirical analysis of the CE 1 reduction effects of ECER policies, with the estimation results presented in Table 3 . Columns (1) to (3) of Table 3 report the estimation results of green fiscal policies on CE 1 . The results show that, when the model does not include control variables, the implementation of green fiscal policies has an estimated coefficient of − 0.070 for CE 1 , significant at the 1% level, indicating that the CE 1 of pilot cities are 7.0% lower than those of non-pilot cities. After adding control variables, the results do not change significantly. Columns (4) to (6) report the estimation results of green fiscal policies on CE 2 . The results indicate that, when the model does not include control variables, the implementation of green fiscal policies has an estimated coefficient of 0.099 for CE 2 , significant at the 1% level, suggesting that the CE 2 of pilot cities is 9.9% higher than that of non-pilot cities. After including control variables, the results remain largely unchanged. This provides evidence for Hypothesis 1: ECER policies have a significant CE 1 reduction effect and also significantly promote CE 2 .
To further illustrate the step-by-step changes in the coefficients, this paper presents Fig. 5 . The horizontal axis of Fig. 5 represents the number of control variables, while the vertical axis indicates the coefficients, with the grey area denoting the error bars. As evident from Fig. 5 , the coefficients and error bars exhibit minimal variation with the increase in control variables, indicating a negligible impact of the number of control variables on the coefficients and highlighting their stability. This finding suggests that the primary regression coefficients remain consistent even when more control variables are included in the analysis, underscoring the model’s robustness.
Plot of coefficient variation based on the step by step method.
The prerequisite for using DID model to evaluate policies is the parallel trends assumption. This implies that, before the policy intervention, the treatment group and the control group should exhibit similar trends without systematic differences. After the policy intervention, the trends between these two groups should diverge significantly. Following existing literature 50 , 59 , 60 , this paper employs an event study approach to analyze the effects before and after the policy implementation.
In Eq. ( 2 ), the variable Treated still represents cities that have been approved to establish pilot ECER policies. To avoid perfect multicollinearity, this paper uses the year before policy implementation as the baseline group, meaning that k = − 1 is not included in the regression equation, and the other parts of the model are consistent with the baseline model. If the coefficient is not significant when k < 0 , it indicates that the estimated results satisfy the parallel trends assumption. Figure 6 shows that, before the implementation of the policy, all coefficients are not significant, and in the fifth year after policy implementation, the coefficients start to become significant. This indicates that the implementation of ECER policies has a significant promotional effect on CE 1 reduction and CE 2 in the pilot areas, but this effect has some lag.
Parallel trend test of CE 1 ( a ) and CE 2 ( b ).
Exclusion of contemporaneous policies.
The smart city construction policy began with the “Notice on Carrying out the National Smart City Pilot Work” issued by the Ministry of Housing and Urban–Rural Development in 2012, with smart city pilots being established in 2012, 2013, and 2014 61 . This paper excludes all smart pilot cities and re-runs the regression, with results shown in columns (1) and (2) of Table 4 . The results indicate that contemporaneous policies during the sample period caused some interference with the estimated coefficients, but the extent is very limited. The implementation of ECER policies still has statistically and economically significant effects on promoting CE 1 reduction and CE 2 in pilot cities.
We employs the Propensity Score Matching (PSM) method to process the data, aiming to reduce data bias and the impact of confounding factors 62 , 63 . Through PSM-DID analysis, the results show that after matching, the absolute bias (|bias|) of all variables decreases by more than 70%, and the p -values are not statistically significant. This comparative analysis reveals the effectiveness of PSM in reducing the initial bias between the treatment and control groups. Therefore, the matching process successfully achieves balance in characteristics between the two groups across key indicators, making the assessment of the treatment effect more accurate and reliable.
Table 4 reports the results of the PSM. The propensity score matching results show a substantial decrease in |bias| for variables, highlighting an enhanced balance between treated and control groups post-matching. For instance, the absolute bias for “lnur” dropped from 86.0% to just 3.3%, showcasing a 96.2% reduction in bias, which underscores the effectiveness of the matching process. Similarly, other variables like “lnfdi”, “lnis”, and “lnsst” experienced significant reductions in bias. The p >|t| values, mostly above 0.05 post-matching, indicate that the differences between groups are not statistically significant, affirming the success of the matching in minimizing discrepancies and improving comparability.
Figure 7 displays the matching results of PSM. The results indicate that after the matching process, the percentage bias (%bias) for the control variables all remain below 10%. This finding fully confirms the effectiveness of the PSM method in balancing key characteristics between the experimental and control groups, thereby ensuring the accuracy and reliability of subsequent analyses.
Balance test.
This paper conducts an empirical analysis using matched data, with the results shown in columns (3) and (4) of Table 5 . The results indicate that ECER policy still has a significant CE 1 reduction effect and also significantly promotes CE 2 . This suggests that there is no significant impact of self-selection bias on the regression results in this study.
To reduce the impact of outliers on regression analysis, this paper adopts a winsorization process 39 , 64 , which involves replacing observations below a certain threshold with the 1st percentile and those above the threshold with the 99th percentile before conducting the regression. Columns (5) and (6) of Table 5 display the analysis results after this treatment, showing that the impact of outliers on the regression results is not significant.
Considering the potential unique impact of the COVID-19 pandemic on CE 1 and CE 2 in 2019, this paper decided to exclude data from 2019 to ensure the robustness of the research results, thus avoiding the interference of pandemic-related outliers in the analysis. Subsequently, the paper conducted an empirical analysis based on the updated dataset, with the analysis results presented in columns (7) and (8) of Table 5 . The analysis results indicate that after excluding the special impact of the COVID-19 pandemic, the CE 1 reduction effect of the green fiscal policy remains significant, and there is still a significant promotional effect on CE 2 .
The DID model is based on the common trends assumption, which posits that, in the absence of an intervention, the trends of the treatment and control groups would have been similar 65 . By conducting a placebo test on data from before the intervention, this assumption can be tested for validity. If significant ‘intervention effects’ are also found during the placebo test conducted before the intervention or at irrelevant time points, this indicates that the effects estimated by DID are actually caused by other unobserved factors, rather than the intervention itself 66 . Referencing the placebo practices in existing literature 59 , this paper tests for the impact of unobservable factors on the estimation results. The study randomizes the impact of ECER policies across cities, selecting treatment groups randomly from 248 cities, with the remaining cities serving as control groups. This randomization process is repeated 500 times to generate a distribution graph of the regression coefficients, where the dashed line in the graph represents the actual regression coefficient, as specifically shown in Fig. 8 . Figure 8 a represents the placebo test for CE 1 , and Fig. 8 b for CE 2 . From Fig. 8 , it is evident that after randomizing the core explanatory variables, the mean of the coefficients is close to 0, and the mean of the coefficients after randomization significantly deviates from their true values. This indicates that, excluding the interference of other random factors on the empirical results, the green fiscal policy has a significant effect on CE 1 reduction and significantly promotes CE 2 .
Placebo test of CE 1 ( a ) and CE 2 ( b ).
The analysis results presented earlier indicate that the ECER policy has significantly promoted CE 1 reduction and the improvement of CE 2 in pilot cities. Accordingly, this study will further explore the mechanism of action of ECER policy and has constructed the following model:
GI refers to green innovation. Following existing literature, this study uses the number of green invention patent grants ( lngi_invention ) and the total number of green patents per 10,000 people ( lnpgi_total ) as proxy variables for green innovation 67 , 68 . Due to the evident causal inference flaws in the three-stage mediation mechanism test 69 , this study refers to the mediation effect test model by Niu et al. 70 and employs the Sobel test to further evaluate the regression results, thereby enhancing the completeness and credibility of the mechanism test 71 . The regression results are shown in Table 6 . Columns (1) and (4) report the impact of the ECER policy on green innovation, with significant results. This confirms hypothesis H2: green fiscal policies can promote CE 1 reduction effects and CE 2 by fostering green innovation. Moreover, the Sobel Z coefficients are greater than 2.58, indicating that the mediating variable has a sufficiently strong explanatory power for the total effect.
By city grade.
In the process of urbanization and industrialization, a city’s level often reflects its level of economic development, capacity for technological innovation, infrastructure completeness, and the comprehensiveness of its public services. This paper categorizes the sample cities based on their tier into higher-level cities (provincial capitals, sub-provincial cities, and municipalities directly under the Central Government) and general cities, and conducts regression analysis. The regression results shown in Table 7 , specifically in columns (1), (2), (6), and (7), indicate that in higher-tier cities, the coefficients of the ECER policy on CE 1 and CE 2 for pilot cities are -0.098 and 0.118, respectively, significant at the 1% level. However, in general cities, the absolute values of the coefficients are smaller and not significant. From this, we can conclude that the ECER policy’s effect on CE 1 reduction and the enhancement of CE 2 is more significant in higher-tier cities compared to general cities. Higher-level cities, with their advanced economic structures, abundant fiscal resources, high levels of technological innovation, and strong policy enforcement capabilities, make the green fiscal policy more effective in these areas in terms of CE 1 reduction and the promotion of CE 2 . Firstly, economically developed higher-tier cities have more sufficient fiscal funds and investment capacity, which can support large-scale green infrastructure construction and green technology R&D, thereby directly reducing urban CE 1 and improving energy use efficiency. Secondly, technological innovation is a key factor in improving CE 2 . As centers of technological innovation and information exchange, higher-level cities are more likely to attract and gather high-tech companies and research institutions, promoting the development and application of green technologies, and effectively reducing CE 1 . Additionally, higher-tier cities usually have more comprehensive laws, regulations, and policy enforcement mechanisms, ensuring the effective implementation and regulation of green fiscal policies. Also, residents in these cities often have higher environmental awareness and a preference for green consumption, which helps to create a favorable social atmosphere for the implementation of green fiscal policies. Finally, due to their strong regional influence and exemplary role, higher-tier cities can promote green transformation and low-carbon development in surrounding areas and even the entire country through policy guidance and market incentives, further amplifying the CE 1 reduction effect and enhancing the impact on CE 2 of green fiscal policies.
Given the significant differences in economic development levels, resource endowments, and institutional environments across regions in China, the implementation effects of the ECER policy may exhibit heterogeneity. Therefore, this paper divides the sample into eastern, central, and western regions for analysis and conducts regressions separately. The regression results are presented in Table 7 . Columns (3) to (5) and (8) to (9) of Table 7 show the regression results for CE1s and CE 2 , respectively, with columns (3) and (8) representing the results for the eastern region. The analysis indicates that, in the eastern region, the ECER policy significantly promotes carbon reduction and CE 2 . Although the policy’s effects in the central region are less than those in the eastern region, they still exhibit a positive impact. In contrast, in the western region, the ECER policy’s promotional effects on carbon reduction and CE 2 are not significant.
This analysis reveals that, within the regional development pattern of China, the eastern regions exhibit more significant outcomes in terms of the CE 1 reduction effect and the enhancement of CE 2 under green fiscal policies compared to the central and western regions. Firstly, as the most economically developed area in China, the eastern region, with its leading total economic output, industrialization, and urbanization levels, provides a solid fiscal support and technological foundation for the implementation of green fiscal policies. This economic advantage enables the eastern region to allocate more resources to the research, development, and application of green technologies, as well as related infrastructure construction, thereby effectively promoting CE 1 reduction and energy efficiency improvement. Secondly, environmental policies and regulations in the eastern region are generally stricter and more advanced. Coupled with a higher public awareness of environmental protection, this creates a favorable social environment and policy atmosphere for the implementation of green fiscal policies and carbon reduction. Additionally, the industrial structure in the eastern region is more optimized and high-end compared to the central and western regions, with a larger proportion of the service industry and high-tech industries, which typically have lower energy consumption intensity and CE 1 , facilitating the improvement of overall CE 2 . Furthermore, as an important gateway for international trade and investment, the eastern region is more open to adopting and introducing advanced green technologies and management practices from abroad, accelerating the pace of green transformation. Lastly, the dense urban network and well-developed transportation and logistics systems in the eastern region provide convenient conditions for the effective implementation of green fiscal policies. Therefore, due to comprehensive advantages in economic development level, industrial structure, policy environment, technological innovation capability, and infrastructure, the eastern region demonstrates more significant performance in the CE 1 reduction effect and the promotion of CE 2 under green fiscal policies.
Figure 9 reports the main regression coefficients and error bars from the heterogeneity analysis, clearly illustrating the distribution of coefficients.
Results of heterogeneity analysis.
Resource-based cities center on industries involved in the extraction and processing of local natural resources, including minerals and forests 72 , 73 , 74 . Due to their unique urban characteristics, these cities may have a specific impact on the efficacy of ECEP policy. Consequently, this paper follows the guidelines set forth by the State Council in the “National Plan for Sustainable Development of Resource-based Cities (2013–2020),” dividing the sample into resource-based and non-resource-based cities for separate regression analyses, the results of which are presented in Table 8 . Columns (1) and (2) detail the regression outcomes for CE 1 , while columns (3) and (4) address CE 2 . The findings reveal that, compared to resource-based cities, the effect of ECEP policies on carbon reduction is more pronounced in non-resource-based cities, with a similarly more substantial impact on the promotion of CE 2 .
Upon conducting a thorough analysis of the disparities in how non-resource-based cities and resource-based cities respond to ECER policies, a significant finding emerges: non-resource-based cities, due to their diversified industrial structures and lower reliance on highly polluting and energy-intensive heavy industries and mineral resource extraction, demonstrate a stronger capacity to adopt and promote new energy, clean energy, and energy-efficient technologies. This characteristic of their industrial structure not only facilitates effective carbon reduction efforts but also propels a shift in economic growth models towards services, high-tech industries, and innovation-driven sectors, which are associated with lower energy consumption and carbon intensities. Therefore, the potential for ECER policies to enhance CE 2 and reduce CE 1 is greater in these cities. In contrast, resource-based cities, due to their long-standing dependence on resource extraction, exhibit significant inertia in their economic structure, technological levels, and employment opportunities. This inertia not only complicates their transition and industrial restructuring but also increases the associated costs. Against this backdrop, non-resource-based cities are more likely to achieve notable successes in implementing ECER policies compared to their resource-based counterparts.
Conclusions.
Based on the city-level dataset from 2003 to 2019, this paper employs a multi-time point difference-in-differences model to thoroughly explore the impact of the ECER policy on CE 1 reduction and CE 2 , reaching the following conclusions:
The ECER policy is confirmed to play a significant role in promoting the reduction of CE 1 and enhancing CE 2 . This conclusion remains robust even after controlling for factors that might affect the accuracy of the assessment, such as contemporaneous policy interferences, sample selection biases, extreme value treatments, and other random factors. This indicates that the ECER policy has important practical implications in mitigating climate change impacts, and its effects are not significantly influenced by the aforementioned potential interferences. The ECER policy effectively promotes CE 1 reduction and CE 2 improvements by incentivizing the research and application of green technologies. This finding underscores the mediating role of green innovation in environmental policies, highlighting that fiscal incentives such as tax breaks and subsidies are crucial for promoting technological innovation and application, and further achieving environmental benefits. The CE 1 reduction effect and CE 2 enhancement of the ECER policy are more pronounced in economically developed, higher-tier cities and in the eastern regions. This may be due to these areas having better infrastructure, higher technological innovation capabilities, more abundant fiscal resources, and stronger public environmental awareness, which all provide strong support for the effective implementation of the ECER policy. Moreover, this variation also suggests that policymakers need to consider regional characteristics when implementing relevant policies to maximize policy effectiveness.
Existing literature has explored the role of energy conservation and emission reduction fiscal policies in environmental protection, such as green credit 37 , ESG performance 75 , green total factor carbon efficiency 36 , and sustainable urban development 38 . These studies report the positive impact of such policies on the environment. However, they do not directly examine the impact of these policies on pollutants. Our study extends the existing literature by investigating the relationship between these policies and carbon emissions. Green fiscal policies significantly promote the reduction of carbon emissions (CE1) and the improvement of carbon efficiency (CE2) through economic incentives, price mechanisms, infrastructure support, and increasing public environmental awareness. Specifically, these policies encourage the research and application of green technologies, change consumer and producer behavior, optimize energy consumption structures, support related infrastructure construction, and increase public participation in low-carbon living. Additionally, green fiscal policies promote sustainable economic growth by directing funds towards low-carbon and green industries, fostering the development of green technologies and industries. Overall, green fiscal policies have not only achieved significant environmental protection results but also played a crucial role in realizing the dual goals of economic growth and environmental protection.
Despite the significant findings, our study has some limitations. Firstly, the data is limited to 248 cities from 2003 to 2019, which may not fully capture the long-term impact of ECER policies. Secondly, reliance on existing data may introduce biases, as not all relevant factors could be considered. Future research could address these limitations by expanding the dataset, including more diverse regions, and employing alternative methods to validate these findings.
Based on the above analysis, the policy recommendations of this paper are as follows:
Continue to increase fiscal support. The government should continue to enhance fiscal support for the ECER policy, including expanding the scope of tax reductions and increasing the level of fiscal subsidies, especially for those projects and technologies that can significantly improve energy efficiency and reduce CE 1 . This will further stimulate the innovation motivation of enterprises and research institutions, accelerating the research and development (R&D) and application of low-carbon technologies.
Optimize policy design and implementation mechanisms. Considering the robustness of the ECER policy effects, the government should further refine the policy design to ensure that measures precisely target sectors and aspects with high CE 1 . Concurrently, it is crucial to establish and enhance the supervision mechanism for policy execution, ensuring effective implementation of policy measures. This approach also necessitates timely adjustments and optimizations of the policy to tackle new challenges effectively.
Establish a dedicated Green Technology Innovation Fund. This fund aims to provide financial support specifically for R&D and promotion of green technologies with high CE 2 . By offering startup capital, R&D subsidies, and rewards for the successful commercialization of green technologies, the fund can not only stimulate the innovation drive of enterprises and research institutions but also accelerate the transformation of green technologies from theory to practice. Consequently, this will promote CE 1 reduction and CE 2 enhancement on a broader scale. This initiative directly responds to the importance of fiscal incentive measures for promoting technological innovation and application emphasized in the research, ensuring the ECER policy maximizes its benefits in promoting green development.
Differentiated policy design. Given the variations in the effects of the ECER policy across different regions, policymakers should design and implement differentiated energy-saving and emission reduction policies based on regional factors such as economic development level, industrial structure, and resource endowment. For economically more developed areas with a stronger technological foundation, CE 1 reduction can be promoted by introducing higher standards for environmental protection and mechanisms for rewarding technological innovation. For regions that are relatively less economically developed, the focus should be on providing technical support and financial assistance to enhance their capacity for CE 1 reduction.
Green fiscal policies play a crucial role in reducing carbon emissions and promoting sustainable economic growth, but their impact on social and income inequality needs careful consideration. Firstly, while policies like carbon taxes are effective in reducing emissions, they may place a significant burden on low-income households, as a larger proportion of their income goes towards energy and basic necessities. To mitigate this inequality, governments can implement redistributive measures, such as using carbon tax revenues for direct subsidies or tax reductions for low-income families, ensuring social equity while achieving emission reductions. Secondly, green fiscal policies encourage investment in green technologies and the implementation of green projects. However, these incentives often favor businesses and wealthy families capable of making such investments, potentially widening income disparities. Therefore, policy design should consider inclusive growth by providing green job training and encouraging small and medium-sized enterprises to participate in green projects, ensuring that various social strata benefit from the green economy. Furthermore, in terms of public investment, governments should prioritize low-income and marginalized communities, ensuring they also benefit from the construction of green infrastructure. This includes prioritizing the development of public transportation and renewable energy projects in these areas, thereby reducing living costs and improving the quality of life for these communities. By adopting these redistributive measures and inclusive policy designs, green fiscal policies can achieve the goals of environmental protection and economic growth while effectively mitigating their negative impacts on social and income inequality, promoting sustainable and inclusive development.
When evaluating various policy tools for achieving carbon reduction goals, it is evident that carbon taxes, renewable energy subsidies, ECER policies, emissions trading systems, and energy efficiency standards each have their unique advantages (see Table 9 ). Carbon taxes leverage price mechanisms to encourage emissions reduction and provide redistribution opportunities, while renewable energy subsidies promote technological advancement and market development. ECER policies offer direct incentives and support for infrastructure, resulting in long-term environmental benefits. Emissions trading systems combine cap-and-trade controls with market flexibility, and energy efficiency standards provide direct pathways to emissions reduction. In practical applications, the integrated use of multiple policy tools, fully utilizing their respective advantages, can more effectively achieve carbon reduction goals and drive the transition to a low-carbon economy. Policymakers must consider equity, economic impact, and public acceptance when designing these policies to balance environmental protection with economic growth. Through careful integration and balanced implementation, green fiscal policies can significantly reduce carbon emissions while promoting sustainable and inclusive economic development.
The datasets used and/or analysed during the current study available from the corresponding author on reasonable request.
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This study is supported by the National Social Science Fund Major Project: “Research on the Policy System and Implementation Path to Accelerate the Formation of New Productive Forces,” Project Number: 23&ZD069.
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Wang, S., Zhang, Z., Zhou, Z. et al. The carbon emission reduction effect of green fiscal policy: a quasi-natural experiment. Sci Rep 14 , 20317 (2024). https://doi.org/10.1038/s41598-024-71728-1
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Caltech economists put supply and demand experiment from 1960s to the test. In an open marketplace, such as a farmers' market where produce and other goods like candles and flowers are exchanged for money, the ideal prices for both consumers and sellers will quickly emerge. For example, if a seller tries to offer a bag of peaches for $10 but ...
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