First Author:   Kazuo Mino Graduate School of Economics, Kobe University mino@econ.kobe-u.ac.jp   Rokkodai, Nada-ku Kobe, 657-8501, Japan   81-78-803-6807(Phone) 81-78-803-6807(Fax) Second Author: Jun-ichi Itaya Graduate School of Economics itaya@econ.hokudai.ac.jp   7 Nishi, Kita-ku Sappro, 060-0890, Japan   81-11-706-2858(Phone) 81-11-706-2858(Fax)