ABSTRACT. We study theoretically and experimentally a committee with common interests. Committee members do not know which of two alternatives is the best, but each member can acquire privately a costly signal before casting a vote under either majority or unanimity rule. In the experiment, as predicted by Bayesian equilibrium, voters are more likely to acquire information under majority rule, and attempt to counter the bias in favor of one alternative under unanimity rule. As opposed to Bayesian equilibrium predictions, however, many committee members vote when uninformed. Moreover, uninformed voting is strongly associated with a lower propensity to acquire information. We show that an equilibrium model of subjective prior beliefs can account for both these phenomena, and provides a good overall fit to the observed patterns of behavior both in terms of rational ignorance and biases. On trouve de plus, que si la probabilité de la voix de chaque Votant est plus grande que 1 2 , c'est-à-dire, s'il est plus probable qu'il jugera conformément à la vérité, plus le nombre des Votans augmentera, plus la probabilité de la vérité de la décision sera grande : la limite de cette probabilité sera la certitude [. . . ] Une assemblée très-nombreuse ne peut pas être composée d'hommes très-éclairés; il est même vraisemblable que ceux qui la forment joindront sur bien des objets beaucoup d'ignorance à beaucoup de préjugés. Condorcet (1785) [1986, p. 29-30]

All sovereign governments face a commitment problem: how can they promise to honor their own agreements? The standard solutions involve reputation or political institutions capable of tying the government's hands. Mexico's government in the 1880s used neither solution. It compensated its creditors by enabling them to extract rents from the rest of the economy. These rents came through special privileges over banking services and the right to administer federal taxes. Returns were extremely high: as long as the government refrained from confiscating all their assets (let alone repaying their debts) less than twice a decade, they would break even.

We conduct a laboratory study of the group-on group ultimatum bargaining with restricted within-group interaction. In this context, we concentrate on the effect of different within-group voting procedures on the bargaining outcomes. Our experimental observations can be summarized in two propositions. First, individual responder behavior across treatments does not show statistically significant variation across voting rules, implying that group decisions may be viewed as aggregations of independent individual decisions. Second, we observe that proposer behavior significantly depends (in the manner predicted by a simple model) on the within-group decision rule in force among the responders and is generally different from the proposer behavior in the one-on-one bargaining.

In a social choice model with an infinite number of agents, there may occur "equal size" coalitions that a preference aggregation rule should treat in the same manner. We introduce an axiom of equal treatment with respect to a measure of coalition size and explore its interaction with common axioms of social choice. We show that, provided the measure space is sufficiently rich in coalitions of the same measure, the new axiom is the natural extension of the concept of anonymity, and in particular plays a similar role in the characterization of preference aggregation rules. JEL D71, C69 * We would like to thank Rajat Deb, John Duggan, Rabee Tourky, and participants at the

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In this paper I provide an example of sorting equilibrium nonexistence in a three-community model of the type introduced in Caplin and Nalebuff (1997; Journal of Economic Theory 72, 306-342). With two communities, such an example has been shown to exist only when the dimension of the policy space is even. It turns out, however, that with three communities existence may fail regardless of whether the policy space dimension is odd or even. This suggests that the original odd/even dichotomy can, at least in part, be explained by the evenness of the number of communities. Copyright 2005 Blackwell Publishing Inc..

Abstract. We analyze existence of divergent equilibrium in a model of endogenous party platforms with stochastic membership. The parties proposals depend on their membership, while the membership depends both on the proposals and the unobserved idiosyncratic preferences of citizens over parties. It is shown that when citizens view the parties as similar, apart from their policy proposals (i.e., the party platform is a good predictor of individual membership decision), the divergent equilibria exist. We analyze the relationship between parties policy proposals and the unobserved idiosyncratic characterisitics of parties and we obtain conclusions different from the ones provided in exisiting literarure.