Jörgen W. Weibull: The Condorcet Jury Problem and Preference Heterogeneity

The talk is based on joint work with Jean-François Laslier (École Polytechnique, Paris).

We consider a committee (board or jury) that faces a binary collective decision under uncertainty, where each member holds some relevant private information. Members agree about what decision should be taken in each state of nature, had this been known. However, this is unknown and members may attach different values to the two types of mistake that may occur.

Standard voting rules have a plethora of uninformative equilibria, and informative voting may even be incompatible with equilibrium. We here generalize existing results with respect to preference heterogeneity across the committee, and also suggest and analyse a randomized majority rule that has a unique equilibrium. This equilibrium is asymptotically efficient: it implements the collectively optimal decision with probability one in the limit as the committee size goes to infinity.