Information About Other Players in Mechanism Design

We show the existence of mechanism design settings where the social planner has an interest in players receiving noisy signals about the types of other agents. When the social planner is interested only in partial implementation, any social choice rule that is incentive compatible after players receive additional information about other agents was originally incentive compatible prior to the change in information structure. However, information about other agents can eliminate undesired equilibria in an implementing mechanism. Thus, there are social choice rules which are not fully implementable in a given information environment that become fully implementable after players have additional information about the types of other agents. We provide some general conditions under which an undesired equilibrium can be eliminated by additional information about other players.