Ambiguity aversion solves the conflict between efficiency and incentive compatibility∗ Luciano De Castroy Nicholas C. Yannelisz First Version: December 2008 This Version: November 2010 Abstract The conflict between Pareto optimality and incentive compatibility, that is, the fact that some Pareto optimal (efficient) allocations are not incen- tive compatible is a fundamental fact in information economics, mechanism design and general equilibrium with asymmetric information. This impor- tant result was obtained assuming that the individuals are expected utility maximizers. Although this assumption is central to Harsanyi’s approach to games with incomplete information, it is not the only one reasonable. In fact, a huge literature criticizes EU’s shortcomings and propose alternative preferences. Thus, a natural question arises: does the mentioned conflict extend to other preferences? We show that when individuals have (a special form of) maximin expected utility (MEU) preferences, then any efficient al- location is incentive compatible. Conversely, only MEU preferences have this property. We also provide applications of our results to mechanism de- sign and show that Myerson-Satterthwaite’s negative result ceases to hold in our MEU framework. Keywords: Asymmetric information, ambiguity aversion, Incentive com- patibility, mechanism design, first-best, second-best. JEL Codes: D50, D81, D82. ∗We are grateful to Marialaura Pesce, Marciano Siniscalchi and Costis Skiadas for helpful conversations. y Department of Managerial Economics and Decision Sciences, Kellogg School of Manage- ment, Northwestern University, Evanston IL 60208. zDepartment of Economics, University of Illinois at Urbana-Champaign and Economics- School of Social Sciences, The University of Manchester. E-mail:
[email protected]. 1 Contents 1 Introduction3 2 Preliminaries6 2.1 Goods and allocations........................6 2.2 Allocations and endowments....................9 2.3 Incentive compatibility......................