Optimal Voting Rules

We derive the incentive compatible and ex-ante welfare maximizing (i.e., utilitarian) mechanism for settings with an arbitrary number of agents and alternatives where the privately informed agents have single-crossing and single-peaked preferences. The optimal outcome can be implemented by modifying a sequential voting scheme, due to Bowen (1943), and used in many legislatures and committees. The modification uses a flexible majority threshold for each of several alternatives, and allows us to replicate, via a single sequential procedure, the entire class of anonymous, unanimous and dominant strategy incentive compatible mechanisms. Our analysis relies on the elegant characterization of this class of mechanisms for single-peaked preferences by Moulin (1980) and, subsequently, for single-crossing preferences by Saporiti (2009).


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