Article History
Received: 21 December 2020
Accepted: 25 February 2021
First Online: 23 March 2021
Competing interests
: The authors declare no competing interests. All data used in this work are obtained from open-source repositories: Ourworldindata.org, Worldometer.info, Citypopulation.de, Data.gouv.fr, Toyokeizai.net.