1. Faculty of Economics Kushiro Public University of Economics Ashino 4‐1‐1, Kushiro‐shi, Hokkaido, Japan and Kobe University Hyogo Japan
2. Faculty of Economics and Business Administration Tokyo Metropolitan University 1‐1 Minami‐Osawa, Hachioji Tokyo Japan
3. Graduate School of Economics Kobe University 2‐1 Rokkodai, Nada, Kobe Hyogo Japan