A characterization of strategy-proof voting rules for separable weak orderings

We consider the problem of choosing a subset of a finite set of indivisible objects (public projects, facilities, laws, etc.) studied by Barbera et al. (1991). Here we assume that agents' preferences are separable weak orderings. Given such a preference, objects are partitioned into three types, "goods", "bads", and "nulls". We focus on "voting rules", which rely only on this partition rather than the full information of preferences. We characterize voting rules satisfying strategy-proofness (no one can ever be better off by lying about his preference) and null-independence (the decision on each object should not be dependent on the preference of an agent for whom the object is a null). We also show that serially dictatorial rules are the only voting rules satisfying efficiency as well as the above two axioms. We show that the "separable domain" is the unique maximal domain over which each rule in the first characterization, satisfying a certain fairness property, is strategy-proof

Good and bad objects: the symmetric difference rule

We consider the problem of ranking sets of objects, the members of which are mutually compatible. Assuming that each object is either good or bad, we axiomatically characterize a cardinality-based rule which arises naturally in this dichotomous setting.

Regrouping of endowments in exchange markets with indivisible goods

In this paper we are interested in efficient and individually rational exchange rules for markets with heterogeneous indivisible goods that exclude the possibility that an agent benefits by regrouping goods in her initial endowment. We present a suitable environment in which the existence of such rules can be analysed, and show the incompatibility of efficiency, individual rationality and regrouping-proofness even if agents' preferences are additive separable.exchange markets, indivisible goods, regrouping-proofness

Dichotomous Preferences and Power Set Extensions

This paper is devoted to the study of how to extend a dichotomous partition of a universal set X into good and bad objects to an ordering on the power set of X. We introduce a family of rules that naturally take into account the number of good objects and the number of bad objects, and provide axiomatic characterizations of two rules for ranking sets in such a context

Dichotomous Preferences and Power Set Extensions

This paper is devoted to the study of how to extend a dichotomous partition of a universal set X into good and bad objects to an ordering on the power set of X. We introduce a family of rules that naturally take into account the number of good objects and the number of bad objects, and provide axiomatic characterizations of two rules for ranking sets in such a context.dichotomy; objects; set extensions; ranking sets

A Maximal Domain for Stragegy-proof and No-vetoer Rules in the Multi-object Choice Model

April 2011, Revised February 201