Key points are not available for this paper at this time.
Zeeshan Khan*a http://orcid.org/0000-0003-1374-0836, Zhu Sisia http://orcid.org/0000-0002-2788-9423 & Yang Siquna http://orcid.org/0000-0001-6539-7289a School of Economics and Management (SEM), Tsinghua University, Beijing, China
Khan et al. (Thu,) studied this question.