The focus of this paper is the endogenous formation of peer groups. In our model agents choose peers before making contributions to public projects, and they differ in how much they value one project relative to another. Thus, the group's preference composition affects the type of contributions...

In several common-value environments (e.g., auctions or elections), players should make informational inferences from opponents' strategies under certain hypothetical events (e.g., winning the auction or being pivotal). We design a voting experiment that identifies whether subjects make these...

We provide a generalization of Harsanyi's (1955) aggregation theorem to the case of incomplete preferences at the individual and social level. Individuals and society have possibly incomplete expected utility preferences that are represented by sets of expected utility functions. Under Pareto...

We study the role of intergroup mobility in the emergence of conflict. Two groups compete for the right to allocate society's resources. We allow for costly intergroup mobility. The winning group offers an allocation, which the opposition can accept or reject, and wage conflict. Agents can also...

Economists are increasingly interested in how group membership affects individual behavior. The standard method assigns individuals to "minimal" groups, i.e. arbitrary labels, in a lab. But real group often involve social interactions leading to social ties between group members. Our experiments...

Behavioral economics has shaken the view that individuals have well-defined, consistent and stable preferences. This raises a challenge for welfare economics, which takes as a key postulate that individual preferences should be respected. We argue, in agreement with Bernheim (2009) and Bernheim...

We consider the spread of a harmful state through a population divided into two groups. Interaction patterns capture the full spectrum of assortativity possibilities. We show that a central planner who aims for eradication optimally either divides equally the resources across groups, or...

We introduce a new distinction between inequality in initial endowments (e.g., ability, inherited wealth) and inequality of what one can obtain as rewards (e.g., prestigious positions, money). We show that, when society allocates resources via tournaments, these two types of inequality have...

We study the design of enforcement mechanisms when enforcement resources are chosen ex ante and are inelastic ex post. Multiple equilibria arise naturally. We identify a new answer to the old question of why non-maximal penalties are used to punish moderate actions: "marginal" penalties are much...

What are the effects of restricting bonded labor clauses in tenancy or debt contracts? While such restrictions reduce agents' ability to credibly commit ex ante to repay principals in states where they default on their financial obligations, they also generate a pecuniary externality on other...