Picking the winners

We analyze the problem of choosing the w contestants who will win a competition within a group of n > w competitors when all jurors commonly observe who the w best contestants are, but they may be biased. We study conditions on the con…guration of the jury so that it is possible to induce the jurors to always choose the best contestants, whoever they are. If the equilibrium concept is dominant strategies, the condition is very strong: there must be at least one juror who is totally impartial, and the planner must have some information about who this juror is. If the equilibrium concept is Nash (or subgame perfect) equilibria the condition is less demanding: for each pair of contestants, the planner must know at least one juror who is not biased in favor/against any of them. Furthermore, the latter condition is also necessary for any other equilibrium concept. We analyze as a speci…c application the case where each juror is biased in favor of one contestant and propose a simple and natural mechanism for this case. Key Words: mechanism design; contests; biased jurors; dominant strategies; Nash equilibrium. J.E.L. Classi…cation Numbers: C72, D71, D78. The author is grateful to L. Corchón and W. Thomson for their valuable suggestions. Financial assistance from Ministerio de Educación y Ciencia under project ECO200803674/ECON, and Junta de Andalucía under project SEJ01645 is gratefully acknowledged. The …nal version of this paper was made while the author was visiting the Department of Economics at the University of Rochester, to which he is grateful for its hospitality. yUniversidad de Málaga, Campus El Ejido, E-29013, Málaga, Spain; tel. +34 95 213 1245, fax: +34 95 213 1299; e-mail: [email protected].