1. 1 Faculty of Economics and Management, Luoyang Institute of Science and Technology , Luoyang 471023 , China .
2. 2 Department of Economics, Faculty of Arts and Social Sciences , National University of Singapore , , Singapore .
3. 3 School of Environmental Engineering and Chemistry, Luoyang Institute of Science and Technology , Luoyang, Henan, 471023 , China .
4. 4 School of Computer and Information Engineering, Luoyang Institute of Science and Technology , Luoyang, Henan, 471023 , China .
5. 5 School of Public Finance and Taxation , Zhongnan University of Economics and Law , Wuhan, Hubei, 430073 , China .