Funding for this research was provided by:
Ministry of Education, Culture, Sports, Science and Technology (18K17633)
Text and Data Mining valid from 2019-06-20
Received: 5 July 2018
Accepted: 6 June 2019
First Online: 20 June 2019
Ethics approval and consent to participate
: Not applicable. No individual data points were used, only agency-level data disclosed by the Ministry were used, based on the Act on Access to Information Held by Administrative Organs in Japan. This study is in line with the Declaration of Helsinki.
: Not applicable.
: The authors declare that they have no competing interests.