Keita Kamei Department of Economics, Seinan Gakuin University   6-2-92 Nishijin, Sawara-ku Fukuoka, 814-8511 Japan   k-kamei@seinan-gu.ac.jp             JEL Areas: L1 : Market Structure, Firm Strategy, and Market Performance: General L4 : Antitrust Issues and Policies: General