Food choices and in particular meat consumption have major impacts on the local and global environment, which is why the topic is gaining attention in environmental economics and other disciplines. In this study, we investigate the effect of increased visibility on food choices, for which there has been little research to date. We present findings from a field experiment among researchers at a large environmental economics conference. When registering for the three-days conference and prior to choosing between vegan, vegetarian, or meat/fish lunches, half of the participants were informed that their choice would be visibly printed on their conference name badge. The remaining half were informed of this saliency only after their food choice (at the conference venue). Despite the conference setting in which environmentally friendly choices and signals are likely to be valued, we find no significant effect of the treatment on lunch choices. We discuss possible reasons for the null effect, including that the consequences of visibility are ignored, discounted, or already factored in.

People do not always lie for personal gain; sometimes, they lie to benefit others whom they are economically dependent on. We investigate this phenomenon in an online experiment with 1,200 Prolific participants, using a principal-agent framework. Principals design contracts that reward agents based on their reporting behavior, while agents have the opportunity to overreport in order to increase the principal’s payout. We implement three experimental treatments that vary whether agents are informed about the potential reward for overreporting or prompted to consider it before making their decision. Our findings show that most principals choose either a generous contract that is independent of the agent’s reporting behavior or a contract that rewards overreporting. While agents are generally reluctant to lie, their willingness to lie increases when the benefits of doing so are made salient or when they are forced to think about them. These results highlight how psychological framing of incentives can influence ethical behavior in economic relationships.

We use an experiment to study the demand for complete and incomplete formal punishment institutions and their ability to promote cooperation. Complete punishment institutions are implemented by the whole group and bind everyone. Incomplete punishment institutions are implemented by a subgroup and bind only the members of this subgroup. We distinguish between strictly incomplete institutions, in which only one subgroup can bind itself while the remaining individuals are unbound, and potentially incomplete institutions, in which two subgroups can bind themselves independently and separately in different institutions, potentially binding everyone. Theoretically, the demand for such formal punishment institutions should depend only on the benefit of cooperation within the group or subgroup bound by the institution. However, we hypothesize and the experimental results confirm that, in the case of incomplete punishment institutions, the benefit of cooperation has a much smaller impact on the demand than in complete punishment institutions. Instead, individuals’ cooperativeness and coordination between the subgroups become important determinants.

As the international community grapples with the complex challenge of climate change, policymakers need reliable data and information to develop effective strategies for reducing greenhouse gas emissions in the business and household sectors. Experimental economics offers a valuable tool for studying human behavior and economic decision-making under controlled conditions and for deriving insights for effective and socially acceptable policy measures. This paper presents contributions from experimental economics to the design and evaluation of climate policy to illustrate important insights and methodological advances.

People often adapt their behavior to the behavior of other people. We test with the help of an experiment whether this also applies to the choice of food and whether the sensitivity regarding others’ behavior increases when the food choice is observable. Participants in the experiment are first-year students who are confronted with different statements about the diets of students already enrolled and studying at the university. Participants then choose between vouchers for vegan, vegetarian, or meat-based foods, with variation as to whether or not this choice is observable. The results show that the overall effects of social norms with and without observability are small and statistically insignificant. This is because women and men respond differently to the interventions; women are much more responsive to social norms than men, especially when their food choice can be observed by others. We discuss how our findings fit with dietary trends and what policy implications they have.

The study of norms is of paramount importance in understanding human behavior. An interdisciplinary literature, using varying definitions and conceptions, shows when and why norms emerge and spread, what form they can take, and how they are enforced. Here, we focus on theoretical and empirical literature that treats norms as a factor influencing human behavior. We first present a new taxonomy of norms, which builds upon and merges previous taxonomies, to distinguish between different types of norms and enforcement mechanisms. We then provide a conceptual framework that identifies reasons for the effects of norms. This framework is based on psychological theories, which serve as a foundation for much of the empirical economic literature measuring norm effects. Finally, we present an overview of empirical economic papers that study the effects of norms on environmentally relevant behavior, as a particularly relevant area for the study of norms. The aim of this overview is to highlight which effects have been insufficiently studied and to give a sense of the potential of norms. This can help policy makers intervene in a more targeted way to address environmental problems.

Using a lab-in-the-field experiment with Ugandan fishers, we study if and how the use of a common pool resource changes when the resource is either scarce or abundant and when the number of users increases over time. Both resource scarcity and a growing group require users to be more constrained, that is, more cooperative, in order to maintain the resource. However, the results show that fishers do not curtail their harvesting behavior under increased pressure, leading to rapid overexploitation when scarce resources are used by a growing group. This implies a particular need for sustainable management when scarce resources are exposed to in-migration.

Analysts have long advocated a linkage between international cooperation on climate change and trade measures, such as border tariffs, as a means of enforcing agreements to achieve deeper cooperation. Nevertheless, it has remained difficult to evaluate whether policy makers will allow such linkages and whether linking climate and trade would, in reality, yield beneficial effects to international cooperation. Working with a large sample of climate experts who are highly experienced in climate diplomacy and policy, we elicited how they view the legitimacy and usefulness of linking trade and climate and what factors can explain those views. We find that experts from richer countries, especially Europe, are more likely to see linkage as legitimate and effective. These experts are particularly likely to favor universal border adjustments (UBAs) that apply to all countries to level the economic playing field, rather than trade measures that define an exclusive “club” of countries making extra efforts to cut emissions while punishing non-club members. This finding reveals tensions between a shift in academic thinking about the value of club-based strategies—including clubs that use border measures for enforcement—and what climate policy experts see as valuable. European experts are particularly likely to favor UBAs and they are also least likely to see risks in implementing trade measures. In general, countries with high quality national institutions see lower risks in using trade measures to enforce greater cooperation on climate change. A particularly robust finding is that experts who perceive their home country’s emissions reduction pledge as ambitious are more likely to see risks from using trade measures. While these are the countries that could benefit the most from using trade measures, they are also the countries that are offering the most under the existing Paris Agreement. Experts seem to be increasingly aware of the dissonance between the voluntarism of the Paris Agreement and growing political pressures to apply trade measures. We also find the attributes of experts, such as training and career experience, can affect their assessments. In some models, experts with economic or business backgrounds are more likely to favor trade measures while those with careers in natural science, diplomacy, and national government are less sanguine. Our results suggest that diverging views on the need for trade-based enforcement are robust, associated with important attributes of countries such as their commitments, and likely to persist—suggesting that policy strategies favoring the use of trade measures must pay close attention to the conditions that will determine where and how trade measures can be implemented. Experts from many countries that are the biggest supporters of the Paris approach to climate cooperation also doubt the legitimacy of trade measures.

Organizations need a better "learning by doing" approach.

Our choice of food has major impacts on the environment. At the same time, it is visible to all people with whom we spend our daily lives. This raises the question of whether people are adapting their diets to gain a green reputation, as has been observed for other environmentally relevant consumption choices. Using an experiment in which participants can choose between vegan, vegetarian, and meat-based food vouchers, we examine how observation by others and the provision of an information nudge influence food choices. The results show that providing an information nudge reduces the likelihood of choosing meat by 12 percentage points. Observation by others does not significantly reduce the likelihood of choosing meat. Contrary to our prediction, when participants are observed and receive the information nudge, they are less inclined to choose one of the more sustainable options. We discuss the reasons for the partly surprising results and the implications for policy.

Enforcement is a challenge for effective international cooperation. In human rights and environmental law, along with many other domains of international cooperation, "naming and shaming" is often used as an enforcement mechanism in the absence of stronger alternatives. Naming and shaming hinges on the ability to identify countries whose efforts are inadequate and effectively shame them toward better behavior. Research on this approach has struggled to identify factors that explain when it influences state behavior in ways that lead to more cooperation. Via survey of a large (N = 910) novel sample of experienced diplomats involved in the design of the Paris Agreement, we find support for the proposition that naming and shaming is most accepted and effective in influencing the behavior of countries that have high-quality political institutions, strong internal concern about climate change, and ambitious and credible international climate commitments. Naming and shaming appears less effective in other countries, so further enforcement mechanisms will be needed for truly global cooperation. We also find that the climate diplomacy experts favor a process of naming and shaming that relies on official intergovernmental actors, in contrast with studies suggesting that NGOs, media, and other private actors are more effective at naming and shaming. We suggest that these tensions-the inability for naming and shaming to work effectively within the countries least motivated for climate action and the preference for namers and shamers that seem least likely to be effective-will become central policy debates around making cooperation on climate change more enforceable.

We use simple theory and an experiment to investigate the decision to link trade cooperation to the provision of a global public good like climate change mitigation. We examine and compare a unilateral approach, in which players decide independently and without commitment, and a multilateral approach, in which players decide by, and are committed through, an agreement. Our theory shows that, if players decide to link unilaterally, in a best case linkage is a coordination game in which equilibrium selection is unreliable. By contrast, if players decide to link multilaterally, selection in this best case is assured by specifying an appropriate participation threshold for the linked agreement to enter into force. Our experimental results confirm the superiority of the multilateral approach and reveal additionally that agreement by a majority coupled with commitment by this majority are required for its success.

In virtually all human societies, the sustained provision of public goods is enforced through punishment. This can happen, for example, via a legal system (formal punishment institutions) or individual-level reciprocity (informal punishment institutions). However, targeting and enforcement of punishment is usually costly, leaving a permanent temptation for individuals to avoid the costs. Here, we show that costly punishment institutions can be adopted through voting and learning but suffer an existential threat if the decision-making process to implement the punishment institution is not aligned with the scale of the public good, creating unavoidable free-riding incentives. We design a model where individuals vote in favour of or against the institution, either with their feet or group vote, to govern public goods at different scales. Learning occurs through the accumulation of one’s experiences and observations of other members in the population, but it may be limited due to memory and information constraints. We show—across scales of the decision-making process and public good—under which conditions punishment institutions are adopted and promote cooperation. Using a meta-study approach, we compare the model to existing experimental results, which largely confirm the key results of the model.

The Paris Agreement on climate change aims to improve cooperation by allowing governments to set their own commitments. Its success hinges on whether governments and investors believe those national commitments. To assess credibility, we interrogate a large novel sample of climate policy elites with decades of experience and well-placed to evaluate whether nations’ policy pledges are aligned with what they are politically and administratively able to implement. This expert assessment reveals that countries making the boldest pledges are also making the most credible pledges, contrasting theoretical warnings of a trade-off between ambition and credibility. We find that the quality of national political institutions is the largest explanator of the variation in credibility, and Europe’s credibility is exceptionally high. We also find that economic factors, such as the costs and benefits of controlling emissions, are statistically unimportant in explaining the credibility of national pledges to cooperate.

We study the social status motive in an experiment at an art-house cinema in Germany where movie-goers can make monetary contributions to help the cinema become climate neutral. Our key result is that offering high contributors a "social status gift" that displays their good deed increases both the likelihood of a high contribution and mean contributions. It performs significantly better than previously studied mechanisms, such as the removal of anonymity, the provision of a reference point, or a neutral thank-you gift, and it also performs better than offering high contributors publicity through social media.

We use a lab-in-the-field experiment to examine how personal experience of good or bad luck and information about the behavior of others influence the risk taking behavior of small-scale fishers in Tanzania. These fishers make many risky decisions in their daily lives, and a better understanding of the factors influencing risky decisions is important from both a policy and scientific perspective. Our results show a slight tendency for fishers to take more risk in a lottery if they have been unlucky in another game shortly before. Risk taking is enhanced by social information when fishers learn that others have taken more risk. This is true although risks are independent and the fishers do not know whether the risk taking of others has ultimately paid off.

In this paper we present a lab-in-the-field experiment with a large and diverse sample to compare charitable donations when individuals decide for themselves only and when they decide as a group representative. In contrast to the previous literature, we find that individuals make greater charitable contributions when they decide as a group representative than when they decide alone. This result demonstrates that being responsible for a group does not always lead to more selfish behavior.

We use an experiment to test the hypothesis that groups consisting of like-minded cooperators are able to cooperate irrespective of punishment and therefore have a lower demand for a costly punishment institution than groups of like-minded free riders, who are unable to cooperate without punishment. We also predict that the difference in the demand for punishment is particularly large when members know about the composition of their group. The experimental results confirm these hypotheses. However, the information about the composition of the group turns out to be even more important than we expected. It helps cooperative groups to avoid wasting resources for an unneeded punishment institution. In uncooperative groups, it helps members to recognize the need for punishment early on and not to follow an uncooperative path that produces a persistently competitive attitude. These findings highlight the role of group composition and information for institution formation.

Polarization on various issues has increased in many Western democracies over the last decades, leading to divergent beliefs, preferences, and behaviors within societies. We develop a model to investigate the effects of polarization on the likelihood that a society will coordinate on a welfare-improving action in a context in which collective benefits are acquired only if enough individuals take that action. We examine the impacts of different manifestations of polarization: heterogeneity of preferences, segregation of the social network, and the interaction between the two. In this context, heterogeneity captures differential perceived benefits from coordinating, which can lead to different intentions and sensitivity regarding the intentions of others. Segregation of the social network can create a bottleneck in information flows about others' preferences, as individuals may base their decisions only on their close neighbors. Additionally, heterogeneous preferences can be evenly distributed in the population or clustered in the local network, respectively reflecting or systematically departing from the views of the broader society. The model predicts that heterogeneity of preferences alone is innocuous and it can even be beneficial, while segregation can hamper coordination, mainly when local networks distort the distribution of valuations. We base these results on a multimethod approach including an online group experiment with 750 individuals. We randomize the range of valuations associated with different choice options and the information respondents have about others. The experimental results reinforce the idea that, even in a situation in which all could stand to gain from coordination, polarization can impede social progress.