Speaker：Dr SUN Yifei (The University of International Business and Economics)

Time：15:30—17:00，March 9，2017

Site：EMS B127

Abstract：Maskin (1977, 1999) proposes a well known monotonicity condition, which we refer to as Maskin monotonicity and shows it to be necessary and almost sufficient for Nash implementation. Although many implementation results using refinements of Nash equilibrium can dispense with Maskin monotonicity, a recent development in the literature shows that if we were to make implementation robust to information perturbations, Maskin monotonicity would come back as a necessary condition. Looking at environments with monetary transfers and quasiliner preferences, we show that Maskin monotonicity is not only necessary but sufficient for Nash implementation by finite mechanisms. It is easy to see that finite mechanisms are robust to information perturbations. To obtain this result, we construct a novel finite mechanism that exploits the notion of dictator lotteries of Abreu and Matsushima (1992) and we apply it to Nash implementation. Our mechanism does not use the integer games or anything alike and takes care of mixed strategies explicitly. We also extend our result to the case of social choice correspondences, two agents, and rationalizable implementation of social choice functions.