1. School of Economics and Management, University of Chinese Academy of Sciences, Beijing 100190, P. R. China
2. Research Center on Fictitious Economy and Data Science, Chinese Academy of Sciences, Beijing 100190, P. R. China
3. Key Laboratory of Big Data Mining and Knowledge Management, Chinese Academy of Sciences, Beijing 100190, P. R. China
4. College of Information Science and Technology, University of Nebraska at Omaha, Omaha, NE 68182, USA