ANONYMITY AND OPTIMALITY OF COMPETITIVE EQUILIBRIA WHEN MARKETS ARE INCOMPLETE

We study the optimality, or efficiency, of competitive equilibria in a standard two period economy where markets are incomplete. Statistical information about consumers' preferences and endowments is known to a social planner, but the planner cannot observe consumers' types directly. A competitive equilibrium is anonymous constrained optimal if the social planner cannot Pareto improve upon the equilibrium allocation by intervening in asset markets with any asset trade rule satisfying anonymity. In some cases, a competitive equilibrium is robustly anonymous constrained optimal, whereas it is known that competitve equilibria are generically constrained suboptimal for the case of completely observable types.