Jun Nagayasu University of Tsukuba   Systems & Information Engineering University of Tsukuba 1-1-1 Tennodai Tsukuba, Ibaraki 305-8573 Japan   nagayasu@sk.tsukuba.ac.jp             JEL Areas: E0 : Macroeconomics and Monetary Economics: General F4 : Macroeconomic Aspects of International Trade and Finance: General