The actions of different agents sometimes reinforce each other. Examples are network effects and the threshold models used by sociologists as well as Harvey Leibensteins's "bandwagon effects." We model such situations as a game with increasing differences, and show that tipping of equilibria,...

This papers investigates the efficiency of aggregate choice in the long run when the individual decision is driven by both personal experience and imitation. Personal experience is represented by choice sets depending upon previous choices. Imitation is modeled first through popularity weighting...

In this paper I apply stochastic stability to compare local information to global information in terms of welfare. Under global information agents potentially imitate anyone else, while under local information choices are grouped into information sets and agents can observe and hence imitate...

This paper studies informal insurance across networks of individuals. Two characteristics are fundamental to the model developed here: First, informal insurance is a bilateral activity, and rarely involves explicit arrangements across several people. Second, insurance is a social activity, and...

This paper studies bilateral insurance schemes across networks of individuals. While transfers are based on social norms, each individual must have the incentive to abide by those norms, and so we investigate the structure of stable insurance networks, in which self-enforcement constraints are...

This paper presents a model of local network effects in which agents connected by a social network each value the adoption of a product by a heterogeneous subset of other agents in their 'neighborhood', and have incomplete information about the structure and strength of adoption...

We propose a model of network games with heterogeneity introduced by endowing players with types that generate preferences among their choices. We study two classes of games: strategic complements or substitutes in payoffs. The payoff function depends on the network structure, and we ask how...

We study the impact of research collaborations in coauthorship networks on total research output. Through the links in the collaboration network researchers create spillovers not only to their direct coauthors but also to researchers indirectly linked to them. We characterize the interior...

We survey the literature on social networks by putting together the economics, sociological and physics/applied mathematics approaches, showing their similarities and differences. We expose, in particular, the two main ways of modeling network formation. While the physics/applied mathematics...

We study the impact of research collaborations in coauthorship networks on research output and how optimal funding can maximize it. Through the links in the collaboration network, researchers create spillovers not only to their direct coauthors but also to researchers indirectly linked to them....