First Author:   Akira Ogawa JSPS Research Fellow ogawa@iss.u-tokyo.ac.jp   2-23-1 Shin-Shiraoka, Shiraoka,, 349-0212, Japan       Second Author: Kazuhiko Kato Graduate School of Economics, University of Tokyo fwin9096@mb.infoweb.ne.jp   7-3-1 Hongo, Bunkyo-ku Tokyo, 113-0033, Japan