Yukio Koriyama

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This paper analyzes the optimal size of a deliberating committee where, (i) there is no con‡ict of interest among individuals, and (ii) information acquisition is costly. The committee members simultaneously decide whether or not to acquire information, and then, they make the ex-post e¢ cient decision. The optimal committee size, k , is shown to be(More)
This work provides necessary and sufficient conditions for the dominance solvability of approval voting games. Our conditions are very simple since they are based on the approval relation, a binary relation between the alternatives. We distinguish between two sorts of dominance solvability and prove that the most stringent one leads to the election of the(More)
We consider a public good provision game with voluntary participation. Agents participating in the game provide a public good and pay the fees according to a mechanism (allocation rule), while non-participants can free-ride on the participants. We examine how the equilibrium public good provision level is a¤ected by enlarging the population of an economy.(More)
It is well known that ex post e¢ cient mechanisms for the provision of indivisible public goods are not interim individually rational. However, the corresponding literature assumes that agents who veto a mechanism can enforce a situation in which the public good is never provided. This paper instead considers majority voting with uniform cost sharing as the(More)
It is commonly accepted that the multiplicity of equilibria is ubiquitous in preference aggregation games with any voting method. We prove that this multiplicity is greatly reduced under some mild restrictions over social preferences when each voter can vote for as many candidates as she wishes (the Approval voting method). For scenarios with three(More)
This paper presents an argument in favor of the “degressive proportionality principle”in apportionment problems. The core of the argument is that each individual derives utility from the fact that the collective decision matches her own will with some frequency, with marginal utility being decreasing with respect to this frequency. Then classical(More)
Cognitive hierarchy models have been developed to explain systematic deviations from the equilibrium behavior in certain classes of games. This paper introduces an endogenous cognitive hierarchy model, which better explains the behavioral heterogeneity of the strategies in games for which the standard cognitive hierarchy model provides an unreasonable(More)
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