We characterize the class of symmetric two-player games in which tit-for-tat cannot be beaten even by very sophisticated opponents in a repeated game. It turns out to be the class of exact potential games. More generally, there is a class of simple imitation rules that includes tit-for-tat but...

We present a model of repeated games in large buyer-seller networks in the presence of reputation networks via which buyers share information about past transactions. The model allows us to characterize cooperation networks - networks in which each seller cooperates (by providing high quality...

The standard theoretical solution to the observation of substantial turnout in large elections is that individuals receive utility from the act of voting. However, this leaves open the question of whether or not there is a significant margin on which individuals consider the effect of their vote...