First Author:   Masatomo Akita Graduate School of Economics, Osaka University akitamasatomo@srv.econ.osaka-u.ac.jp   1-7 Machikaneyama Toyonaka, 560-0043, Japan       Second Author: Yusuke Osaki Faculty of Economics, Osaka Sangyo University osaki@eco.osaka-sandai.ac.jp   , 574-8530, Japan