1. Department of Social Statistics, University of Manchester, HBS Building, Oxford Road, Manchester M13 9PL, UK
2. Warwick Manufacturing Group, The University of Warwick, Coventry CV4 7AL, UK
3. Independent Researcher, Chongqing 400000, China
4. Faculty of Science and Technology, Beijing Normal University-Hong Kong Baptist University United International College (UIC), Zhuhai 519000, China