First Author:   Yoshihiko Tsukuda Tohoku University tsukuda@econ.tohoku.ac.jp         Second Author: Tatsuyoshi Miyakoshi Osaka University miyakoshi@osipp.osaka-u.ac.jp   Machikaneyama-machi, Machikaneyama-machi Toyonaka, 560-0043, JAPAN   +81-6-6850-5638(Phone) +81-6-6850-5656(Fax) http://www2.osipp.osaka-u.ac.jp/~miyakoshi/indexe.htm