Social norms and choice: a weak folk theorem for repeated matching games

A folk theorem for repeated matching games is established that holds if the stage game is not a pure coordination game. It holds independent of population size and for all matching rules—including rules that depend on players choices or the history of play. This paper also establishes an equilibrium condition and using this discovers two di¤erences between the equilibria of repeated matching games and standard repeated games. Trigger strategies are not equilibria and there is no simple optimal penal code.