This research is supported by the Ministry of Education in China (MOE) Project of Humanities and Social Sciences (18YJC790166), the Innovation and Talent Base for Digital Technology and Finance (B21038) and Digital Technology and Financial Engineering Discipline Construction Fund and the Fundamental Research Funds for the Central Universities (Zhongnan University of Economics and Law). All remaining errors are our own. We thank the editor and the anonymous reviewers for their insightful comments and suggestions.