Mouhua Liao Xiamen University   A123 Econ Building Xiamen University Xiamen, Fujian 361005 China   mouhualiao@gmail.com   http://wise.xmu.edu.cn/people/faculty/ea2e465b-2d68-4b7f-b036-01ff095a0b5d.html           JEL Areas: J6 : Mobility, Unemployment, and Vacancies: General D4 : Market Structure and Pricing: General