1. Institute for Financial Studies, Shandong University, Jinan 250100, Shandong, P. R. China
2. University of Toronto, Toronto, Ontario, Canada M5S 1A1, Canada
3. Institute for Financial Studies and Shandong Province Key Laboratory of Financial Risk, Shandong University, Jinan 250100, Shandong, P. R. China
4. Zhongtai Futures Co., Ltd, Jinan 250001, Shandong, P. R. China