First Author:   Toshihiro Matsumura Institute of Social Sciences, University of Tokyo matsumur@iss.u-tokyo.ac.jp   7-3-1, Hongo Bunkyo-ku, 113-0053, Japan   81-3-5841-4932(Phone) 81-3-5841-4932(Fax) Second Author: Akira Ogawa College of Liberal Arts, International Christian University ogawaa@icu.ac.jp   3-10-2, Osawa Mitaka-city, 181-8585, Japan