Strategy-Proofness in Domains of Lexicographic Preferences: A Characterization

• Authors: Pietro Salmaso, Bernardo Moreno and Dolors Berga
• BSE Working Paper: 1541 | December 25
• Keywords: anonymity , lexicographic preferences , strategy-prooofnes , sequential rules by committee , Condorcet winner
• JEL codes: D71, D72

We assume that a finite set of alternatives can be described by an ordered set of characteristics and offer a general version of lexicographicity that incorporates the possibility that agents’ preferences over characteristics are not separable (the desirability of a characteristic does not depend on other characteristics). We first characterize all strategy-proof rules as a family of sequential rules by committees, with the particularity that the committee used in the decision over each characteristic may depend on the decision about previous ones. Our characterization does not require imposing voter sovereignty and the rules may incorporate restrictions over the alternatives to be selected. Then, we obtain the subclass of anonymous rules that where the committees are quota committees. Finally, we demonstrate that the only anonymous and strategy-proof rules that select a Condorcet winner are the subclass of sequential rules by majority (quota) committees.