Hongfei Ye:  Hongfei Ye，Postgraduate，Department of Economics，National University of Singapore，Singapore.

Yun Wang:  Yun Wang，Corresponding author，Assistant Professor，Wang Yanan Institute for Studies in Economics，Xiamen University，Xiamen361005，China.

Shaomin Huang:  Shaomin Huang，Professor of Economics，Dean，International School of Business，Beijing International Studies University，Beijing 100024，China.