1. Division of Mathematical Science for Social Systems, Graduate School of Engineering Science, Osaka University, 1-3, Machikaneyama-cho, Toyonaka, Osaka 560-8531, Japan
2. Graduate School of Economics, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
3. Mitsubishi UFJ Trust Investment Technology Institute Co., Ltd. (MTEC), 2-6, Akasaka 4-Chome, Minato, Tokyo 107-0052, Japan