Shigehiro Serizava University of Osaka   Institute of Social and Economic Research Osaka University 6-1, Mihogaoka Ibaraki, Osaka 567-0047 JAPAN   serizawa@iser.osaka-u.ac.jp   http://www.iser.osaka-u.ac.jp/~serizawa/           JEL Areas: C7 : Game Theory and Bargaining Theory:General