One Person, Many Votes: Divided Majority and Information Aggregation

Authors

  • Laurent Bouton,

    1. Dept. of Economics, Boston University, 270 Bay State Road, Boston, MA 02215, U.S.A.; lbouton@bu.edu
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  • Micael Castanheira

    1. ECARES, Université Libre de Bruxelles, CP114/4, 50 avenue F.D. Roosevelt, 1050 Brussels, Belgium; mcasta@ulb.ac.be
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    • We thank a co-editor and three anonymous referees. We also thank David Austen-Smith, Steve Brams, Tim Feddersen, Howard Margolis, Cesar Martinelli, Margaret Meyer, Roger Myerson, and Nicola Persico, as well as our colleagues at ULB and BU. We benefited from the comments of the audiences at ESSIT 2007, the PSPE Conference on Institutions at LSE, the Political Economy of Democracy Workshop in Barcelona, the Journées Gérard-Varet 2008, Games 2008, ESEWM 2008, at the Universities of Toulouse, Louvain, Essex, Rotterdam, Chicago, Toronto, Carlos 3 de Madrid, Autonoma de Barcelona, at the Paris School of Economics, Kellogg, Harvard/MIT, Ecole Polytechnique, and HEC Montreal. Micael Castanheira is FNRS research fellow and he thanks them for their financial support. All remaining errors are our own.


Abstract

This paper shows that information imperfections and common values can solve coordination problems in multicandidate elections. We analyze an election in which (i) the majority is divided between two alternatives and (ii) the minority backs a third alternative, which the majority views as strictly inferior. Standard analyses assume voters have a fixed preference ordering over candidates. Coordination problems cannot be overcome in such a case, and it is possible that inferior candidates win. In our setup the majority is also divided as a result of information imperfections. The majority thus faces two problems: aggregating information and coordinating to defeat the minority candidate. We show that when the common value component is strong enough, approval voting produces full information and coordination equivalence: the equilibrium is unique and solves both problems. Thus, the need for information aggregation helps resolve the majority's coordination problem under approval voting. This is not the case under standard electoral systems.

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