This paper studies which social networks maximize trust and cooperation when agreements are implicitly enforced. We study a repeated trust game in which trading opportunities arise exogenously and the social network determines the information transmission technology. We show that cohesive communities, modeled as social networks of complete components, emerge as the optimal community design. Cohesive communities generate some degree of common knowledge of transpired play that allows players to coordinate their punishments and, as a result, yield relatively high equilibrium payoffs. Our results provide an economic rationale for the commonly argued optimality of cohesive social networks.
JEL classification numbers: D85, C73, L14, D8.
Keywords: cohesiveness., coordination, information transmission, repeated games, social networks