1. Department of Statistics, University of Illinois at Urbana-Champaign, Champaign, IL;;
2. Department of Statistics, University of California, Irvine, Irvine, CA;;
3. Gies College of Business, University of Illinois at Urbana-Champaign, Champaign, IL;;
4. College of Business, City University of Hong Kong, Kowloon, Hong Kong