Funding for this research was provided by:
Humanities and Social Science Fund of Ministry of Education of China (No. 15JJD630009)
Received: 8 August 2020
Accepted: 26 November 2020
First Online: 19 February 2021
Ethics approval and consent to participate
: The data used in this study were retrieved from the CHARLS. This survey was endorsed by the Biomedical Ethics Committee of Peking University (NO. IRB00001052–11015). All participants in the survey signed or marked (if illiterate) the informed consent forms.
: Not applicable
: The authors declare that they have no competing interests.