Funding for this research was provided by:
The Top Global University Project from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan
Received: 12 August 2020
Accepted: 23 October 2020
First Online: 16 November 2020
Ethics approval and consent to participate
: Mercari, Inc. approved the use of the data for the present study under the condition that the data were hashed and only released to the collaborators of the project (i.e., the first and last authors, because the second and third authors are employees of the company).
: The second and third authors are employees of the company that provided the data analysed in the present manuscript. However, this fact does not cause any conflict of interest because the analyses, results and their interpretation are free of any bias towards the merit of the company.