Hao, Yuanyuan
Article History
Received: 14 October 2022
Accepted: 29 March 2023
First Online: 11 April 2023
Competing interests
: The author declares no competing interests.
: This research was not required to receive any ethical approval because it did not involve human research participants and no primary data were collected. It uses data collected by statistical organizations such as the National Bureau of Statistics of China and the World Bank.
: This article does not contain any studies with human participants performed by any of the author(s).