DP6695 One Person, Many Votes: Divided Majority and Information Aggregation

Author(s): Laurent Bouton, Micael Castanheira
Publication Date: February 2008
Keyword(s): Approval Voting, Information Aggregation, Multicandidate Elections, Poisson Games
JEL(s): C72, D72, D81, D82
Programme Areas: Public Economics
Link to this Page: cepr.org/active/publications/discussion_papers/dp.php?dpno=6695

This paper compares the properties of three electoral systems when voters have imperfect information. Imperfect information blurs voter decisions and may divorce the electoral outcome from the true preferences of the electorate. The challenge for electoral design is therefore to translate the (sometimes contradictory) elements of information dispersed in the electorate into the most efficient aggregate outcome. We propose a novel model of multi-candidate elections in Poisson games, and show that Approval Voting produces a unique equilibrium that is fully efficient: the candidate who wins the election is the one preferred by a majority of the electorate under full information. By contrast, traditional systems such as Plurality and Runoff elections cannot cope satisfactorily with information imperfections.