1. College of Economics and Management, China Agricultural University, Beijing, China
2. Department of Economics, Western University (UWO), London, Ontario, Canada
3. National Bureau of Economic Research (NBER), Cambridge, MA, USA
4. Research Center for International Trade and Economics, Guangdong University of Foreign Studies (GDUFS), No. 2 Baiyun Avenue North, Baiyun District, Guangzhou, Guangdong 510420, China
5. Research Center for International Trade and Economics, Guangdong University of Foreign Studies (GDUFS) , No. 2 Baiyun Avenue North, Baiyun District, Guangzhou, Guangdong 510420, China