Coalition-Proof Nash Equilibria I: Concepts

In an important class of “noncooperative” environments, it is natural to assume that players can freely discuss their strategies, but cannot make binding commitments. In such cases, any meaningful agreement between the players must be self-enforcing. Although the Nash best-response property is a necessary condition for self-enforceability, it is not sufficient—it is in general possible for coalitions arrange plausible, mutually beneficial deviations from Nash agreements. We provide a stronger definition of self-enforceability, and label the class of efficient self-enforcing agreements “coalition-proof.”