Zequn Ye Graduate School of Economics, Nagoya University   Graduate School of Economics, Nagoya University Furo-Cho Chikusa Ward Nagoya, Aichi 464-8601 Japan   ye.zequn.h8@s.mail.nagoya-u.ac.jp             JEL Areas: J2 : Demand and Suppply of Labor: General O3 : Technological Change; Research and Development: General