Jinghong Gu Faculty of Economics, Saga University, 1 Honjo-machi, Saga, 840-8502, Japan.   1 Honjo-machi Saga, Saga 840-8502 Japan   koku@cc.saga-u.ac.jp             JEL Areas: J6 : Mobility, Unemployment, and Vacancies: General O3 : Technological Change; Research and Development: General