Ken-Ichi Akao Waseda University, JApan   1-6-1 Nishiwaseda Shijuku Tokyo, 169-8050 Japan   akao@waseda.jp   http://www.f.waseda.jp/akao/KA/Kenichi_Akao.htm           JEL Areas: C : Mathematical and Quantitative Methods D9 : Intertemporal Choice and Growth: General