1. School of Law, Zhejiang University of Finance and Economics, Hangzhou 310018, P. R. China
2. Department of Statistics, Stanford University, Stanford, CA 94305-4065, USA
3. School of Accounting, Zhejiang University of Finance and Economics, Hangzhou 310018, P. R. China
4. School of Finance and Coordinated Innovation Center of Wealth Management and Quantitative Investment, Zhejiang University of Finance and Economics, Hangzhou 310018, P. R. China
5. School of Information Engineering, Nanchang Hangkong University, Nanchang 330063, P. R. China
6. School of Business and Research Center for Econophysics, East China University of Science and Technology, Shanghai 200237, P. R. China