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Committee decisions: Optimality and Equilibrium


  • Jean-François Laslier

    (Department of Economics, Ecole Polytechnique - Polytechnique - X - CNRS - Centre National de la Recherche Scientifique)

  • Jörgen Weibull

    (Department of Economics, Ecole Polytechnique - Polytechnique - X - CNRS - Centre National de la Recherche Scientifique, SSE - Department of Economics - Stockholm School of Economics)


We consider a group or committee that faces a binary decision under uncertainty. Each member holds some private information. Members agree which decision should be taken in each state of nature, had this been known, but they may attach different values to the two types of mistake that may occur. Most voting rules have a plethora of uninformative equilibria, and informative voting may be incompatible with equilibrium. We analyze an anonymous randomized majority rule that has a unique equilibrium. This equilibrium is strict, votes are informative, and the equilibrium implements the optimal decision with probability one in the limit as the committee size goes to infinity. We show that this also holds for the usual majority rule under certain perturbations of the behavioral assumptions: (i) a slight preference for voting according to one's conviction, and (ii) transparency and a slight preference for esteem. We also show that a slight probability for voting mistakes strengthens the incentive for informative voting.

Suggested Citation

  • Jean-François Laslier & Jörgen Weibull, 2008. "Committee decisions: Optimality and Equilibrium," Working Papers halshs-00121741, HAL.
  • Handle: RePEc:hal:wpaper:halshs-00121741
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    References listed on IDEAS

    1. McLennan, Andrew, 2011. "Manipulation in elections with uncertain preferences," Journal of Mathematical Economics, Elsevier, vol. 47(3), pages 370-375.
    2. Bauke Visser & Otto H. Swank, 2007. "On Committees of Experts," The Quarterly Journal of Economics, Oxford University Press, vol. 122(1), pages 337-372.
    3. Kfir Eliaz, 2002. "Fault Tolerant Implementation," Review of Economic Studies, Oxford University Press, vol. 69(3), pages 589-610.
    4. Hans Gersbach & Volker Hahn, 2008. "Should the individual voting records of central bankers be published?," Social Choice and Welfare, Springer;The Society for Social Choice and Welfare, vol. 30(4), pages 655-683, May.
    5. Hahn, Volker, 2008. "Committees, sequential voting and transparency," Mathematical Social Sciences, Elsevier, vol. 56(3), pages 366-385, November.
    6. Sah, Raaj Kumar & Stiglitz, Joseph E, 1988. "Committees, Hierarchies and Polyarchies," Economic Journal, Royal Economic Society, vol. 98(391), pages 451-470, June.
    7. Feddersen, Timothy J & Pesendorfer, Wolfgang, 1996. "The Swing Voter's Curse," American Economic Review, American Economic Association, vol. 86(3), pages 408-424, June.
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    9. Myerson, Roger B., 1998. "Extended Poisson Games and the Condorcet Jury Theorem," Games and Economic Behavior, Elsevier, vol. 25(1), pages 111-131, October.
    10. Nicola Persico, 2004. "Committee Design with Endogenous Information," Review of Economic Studies, Oxford University Press, vol. 71(1), pages 165-191.
    11. Dixit, Avinash & Weibull, Jörgen, 2006. "Political Polarization," SSE/EFI Working Paper Series in Economics and Finance 655, Stockholm School of Economics, revised 19 Apr 2007.
    12. repec:cup:apsrev:v:90:y:1996:i:01:p:34-45_20 is not listed on IDEAS
    13. Ruth Ben-Yashar & Igal Milchtaich, 2007. "First and second best voting rules in committees," Social Choice and Welfare, Springer;The Society for Social Choice and Welfare, vol. 29(3), pages 453-486, October.
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    15. Wit, Jorgen, 1998. "Rational Choice and the Condorcet Jury Theorem," Games and Economic Behavior, Elsevier, vol. 22(2), pages 364-376, February.
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    17. Job Swank & Otto H. Swank & Bauke Visser, 2008. "How Committees of Experts Interact with the Outside World: Some Theory, and Evidence from the FOMC," Journal of the European Economic Association, MIT Press, vol. 6(2-3), pages 478-486, 04-05.
    18. Gerardi, Dino & Yariv, Leeat, 2007. "Deliberative voting," Journal of Economic Theory, Elsevier, vol. 134(1), pages 317-338, May.
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    Cited by:

    1. Bezalel Peleg & Shmuel Zamir, 2009. "On Bayesian-Nash Equilibria Satisfying the Condorcet Jury Theorem: The Dependent Case," Discussion Paper Series dp527, The Federmann Center for the Study of Rationality, the Hebrew University, Jerusalem.
    2. Tovey, Craig A., 2010. "The instability of instability of centered distributions," Mathematical Social Sciences, Elsevier, vol. 59(1), pages 53-73, January.
    3. Bezalel Peleg & Shmuel Zamir, 2008. "Condorcet Jury Theorem: The Dependent Case," Levine's Working Paper Archive 122247000000002115, David K. Levine.

    More about this item


    Voting; Condorcet; committee; judgement aggregation.; judgement aggregation;

    JEL classification:

    • D71 - Microeconomics - - Analysis of Collective Decision-Making - - - Social Choice; Clubs; Committees; Associations
    • D72 - Microeconomics - - Analysis of Collective Decision-Making - - - Political Processes: Rent-seeking, Lobbying, Elections, Legislatures, and Voting Behavior

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