CIRJE-F-395. Kandori, Michihiro, "Repeated Games, Entry in The New Palgrave Dictionary of Economics, 2nd Edition", January 2006.

This entry shows why self-interested agents manage to cooperate in a long-term relationship. When agents interact only once, they often have an incentive to deviate from cooperation. In a repeated interaction, however, any mutually beneficial outcome can be sustained in an equilibrium. This fact, known as the folk theorem, is explained under various information structures. This entry also compares repeated games with other means to achieve efficiency and briefly discuss the scope for potential applications.