Keisuke Otsu Keio University   2-15-45 Mita Keio University Faculty of Business and Commerce Minato-Ku, Tokyo 108-8345 日本   k.otsu@fbc.keio.ac.jp             JEL Areas: E1 : General Aggregative Models: General E3 : Prices, Business Fluctuations, and Cycles: General (includes Measurement and Data)