UNANIMOUS IMPLEMENTATION: A CASE FOR APPROVAL MECHANISMS

Matias Nunez (1) , Dimitrios Xefteris (2)

1 Université Paris Dauphine-PSL
2 UCY - University of Cyprus [Nicosia]

We design the class of (indirect) Approval mechanisms which allow the players’ strategies to coincide with the subsets of the outcome space. By focusing on the single-peaked domain, we prove that: a) Each of these mechanisms is characterized by a unique equilibrium outcome, and b) for almost every implementable welfare optimum (outcome of a social choice rule), including the Condorcet winner alternative, there exists an Approval mechanism that unanimously implements it. That is, Approval mechanisms help a society achieve every feasible welfare goal, and, perhaps more importantly, they promote social coherence: The implemented outcome is approved by everyone.

Mots clés: Indirect Mechanisms; Nash Implementation; Strategy-proof; Unanimity

Domaines: Économie et finance quantitative [q-fin]

Matias Nunez, Dimitrios Xefteris. UNANIMOUS IMPLEMENTATION: A CASE FOR APPROVAL MECHANISMS . 2016. ⟨hal-01270275v2⟩