This paper builds a theory of informal contract enforcement in social networks. In our model, relationships between individuals generate social collateral that can be used to control moral hazard when agents interact in a borrowing relationship. We define trust between two agents as the maximum...

"We develop a model of informal risk-sharing in social networks, where relationships between individuals can be used as social collateral to enforce insurance payments. We characterize incentive compatible risk-sharing arrangements and obtain two results. (1) The degree of informal insurance is...

We conduct field experiments in a large real-world social network to examine why decision-makers treat their friends more generously than strangers. Subjects are asked to divide a surplus between themselves and named partners at varying social distances, but only one of these decisions is...

We combine information on social networks with medical records and survey data in order to examine how friends affect one's decision to get vaccinated against the flu. The random assignment of undergraduates to residential halls at a large private university allows us to estimate how peer...

We conduct field experiments in a large real-world social network to examine why decision makers treat friends more generously than strangers. Subjects are asked to divide surplus between themselves and named partners at various social distances, where only one of the decisions is implemented....