Chunhui Wen acknowledges the support from the National Social Science Foundation of China (#13CJY008), Postdoctoral Foundation of China (#2016M591642), Social Science Foundation of Hunan Province (#15YBA206) and 1515 Talents Project of Hunan Agricultural University. Xin Xia acknowledges the support from the National Natural Science Foundation of China (#71402087 and #71472117). Jinqiang Yang acknowledges the support from the National Natural Science Foundation of China (#71202007, #71522008, #71532009 and #71573033), Innovation Program of Shanghai Municipal Education Commission (#13ZS050), Chen Guang Project of Shanghai Municipal Education Commission and Shanghai Education Development Foundation (#12CG44), Innovative Research Team of Shanghai University of Finance and Economics (#2016110241), and Fok Ying-Tong Education Foundation of China (#151086).