First Author:   Roki Iwahashi Graduate School of Economics, Kyoto University roki@economics.mbox.media.kyoto-u.ac.jp   Yoshida-hommachi, Sakyo-ku , 606-8501, Japan       http://www.geocities.co.jp/Stylish-Modern/3277/ Second Author: Tomohiro Machikita Institute of Economic Research, Hitotsubashi University machi@ier.hit-u.ac.jp   2-1 Naka Kunitachi, 186-8603, Japan       http://www.ier.hit-u.ac.jp/~machi/