De la manipulation des élections indirectesJournal articleSebastian Bervoets and Vincent Merlin, Revue Économique, Volume 58, Issue 3, pp. 767-777, 2007

This paper is devoted to the analysis of two tiers voting rules. First, one candidate is elected in every jurisdiction and next, an aggregation procedure collects the results from the jurisdictions in order to designate the final winner. It appears that whenever individuals are allowed to change jurisdiction when casting their ballot, it is possible that they can manipulate the result of the election, except when the voting rule is the Priority rule, which assigns a priority order to the candidates. Classification JEL : D71, D72

Appraising diversity with an ordinal notion of similarity: An axiomatic approachJournal articleSebastian Bervoets and Nicolas Gravel, Mathematical Social Sciences, Volume 53, Issue 3, pp. 259-273, 2007

This paper provides an axiomatic characterization of two rules for comparing alternative sets of objects on the basis of the diversity that they offer. The framework considered assumes a finite universe of objects and a priori given ordinal quadernary relation that compares alternative pairs of objects on the basis of their ordinal dissimilarity. Very few properties of this quadernary relation are assumed (beside completeness, transitivity and a very natural form of symmetry). The two rules that we characterize are the maxi max criterion and the lexi-max criterion. The maxi max criterion considers that a set is more diverse than another if and only if the two objects that are the most dissimilar in the former are weakly as dissimilar as the two most dissimilar objects in the later. The lexi-max criterion is defined as usual as the lexicographic extension of the maximax criterion.

Freedom of choice in a social context: comparing game formsJournal articleSebastian Bervoets, Social Choice and Welfare, Volume 29, Issue 2, pp. 295-315, 2007

In this paper we introduce the set of outcomes of game forms as the relevant attribute for evaluating freedom of choice. These sets are defined as the cartesian product of every individual’s set of available options. It is argued that doing so is one way of taking into account social interactions when evaluating individual freedom. A set of axioms is introduced that convey some intuitions about how interactions affect freedom of choice. Using these axioms, two criteria are characterized for comparing game forms in terms of the freedom of choice they offer, the Max and the MaxMin. These criteria are based respectively on the comparison of the best and the worse outcome the individual can reach in the game form.