I consider markets in which participants have very little information: for instance, agents are anonymous, cannot verify each other’s identities, or have little information about each other’s past transactions. I ask whether it is possible to prevent opportunistic behavior in such settings in the absence of contractual enforcement. I model such markets as repeated anonymous-random-matching games and show that cooperation is sustainable if players are sufficiently patient and can announce their name (though unverifiable) before every transaction. Cooperation is achieved by “community responsibility”: if a player deviates, her entire community is held responsible and punished by the victim. Sustaining cooperation involves partial authentication of identities by checking players’ knowledge about past transactions.

We study a canonical collective action game with incomplete information. Individuals attempt to coordinate to achieve a shared goal, while also facing a temptation to free-ride. More similar information can help them coordinate, but it can also exacerbate free-riding. Our main result shows that more similar information facilitates (impedes) achieving the common goal when it is sufficiently challenging (easy). We apply this insight to show why less powerful authoritarian governments may face larger protests if they restrict press freedom, when committee diversity is beneficial in costly voting, and when a more diverse community contributes more to public good provision. (JEL C71, D71, D72, D81, D82, D83, H41)

We consider bargaining environments in which public opinion provides leverage by making compromises costly. Two parties make initial demands, before knowing the public opinion. If deadlocked, they can bargain again after public opinion forms, but suffer reputation costs if they compromise, i.e., scale back their demands. We show that in equilibrium, parties may choose to make incompatible demands initially and gamble over public opinion even though one or both parties must bear a cost later. We characterize when deadlocks arise, and how this affects the welfare of the public in a representative two-party democracy compared to a direct democracy. (JEL C78, D72)

We prove the folk theorem for discounted repeated games with anonymous random matching. We allow non‐uniform matching, include asymmetric payoffs, and place no restrictions on the stage game other than full dimensionality. No record‐keeping or communication devices—including cheap talk communication and public randomization—are necessary.

We study a dynamic contribution game where investors seek private benefits offered in exchange for contributions, and a single, publicly minded donor values project success. We show that donor contributions serve as costly signals that encourage socially productive contributions by investors who face a coordination problem. Investors and the donor prefer different equilibria, but all benefit in expectation from the donor’s ability to dynamically signal his valuation. We explore various contexts in which our model can be applied and delve empirically into the case of Kickstarter. We calibrate our model and quantify the coordination benefits of dynamic signaling in counterfactuals. (JEL C73, D26, D82, G32, L26, M13)