Choosing How to Choose: Self Stable Majority Rules

We consider the endogenous choice of a voting rule, characterized by the majority size needed to elect change over the status quo, by a society who will use the rule to make future decisions. Under simple assumptions on the uncertainty concerning the future alternatives that will be voted upon, voters' have induced preferences over voting rules that are single-peaked and intermediate. We explore the existence of self-stable voting rules, i.e., voting rules such that there is no alternative rule that would beat the given voting rule if the given voting rule is used to choose between the rules. There are situations where self-stable voting rules do not exist. We explore conditions that guarantee existence, as well as issues relating to efficiency and constitutional design.

And the loser is... Plurality Voting

This paper reports on a vote for choosing the best voting rules that was organized among the participants of the Voting Procedures workshop in July, 2010. Among 18 voting rules, Approval Voting won the contest, and Plurality Voting received no support at all.

Variable-population voting rules

Let X be a set of social alternatives, and let V be a set of `votes' or `signals'. (We do not assume any structure on X or V). A `variable population voting rule' F takes any number of anonymous votes drawn from V as input, and produces a nonempty subset of X as output. The rule F satisfies `reinforcement' if, whenever two disjoint sets of voters independently select some subset Y of X, the union of these two sets will also select Y. We show that F satisfies reinforcement if and only if F is a `balance rule'. If F satisfies a form of neutrality, then F is satisfies reinforcement if and only if F is a scoring rule (with scores taking values in an abstract linearly ordered abelian group R); this generalizes a result of Myerson (1995). We also discuss the sense in which the balance or scoring representation of F is unique. Finally, we provide a characterization of two scoring rules: `formally utilitarian' voting and `range voting'. areinforcement; scoring rule; balance rule; linearly ordered abelian group; formal utilitarian; range voting

Optimal Voting Rules

We study dominant strategy incentive compatible (DIC) and deterministic mechanisms in a social choice setting with several alternatives. The agents are privately informed about their preferences, and have single-crossing utility functions. Monetary transfers are not feasible. We use an equivalence between deterministic, DIC mechanisms and generalized median voter schemes to construct the constrained-efficient, optimal mechanism for an utilitarian planner. Optimal schemes for other welfare criteria such as, say, a Rawlsian maximin can be analogously obtained