First Author:   Daisuke Shimizu Graduate School of Economics, University of Tokyo dshimizu@grad.e.u-tokyo.ac.jp   7-3-1 Hongo, Bunkyo-ku Tokyo, 113-0033, Japan   (81)-47-326-2505(Phone) (81)-47-326-2505(Fax) Second Author: Toshihiro Matsumura Institute of Social Science, University of Tokyo matsumur@iss.u-tokyo.ac.jp