According to education ministry statistics, the number of people who completed a doctoral course in the 2018 school year totaled 15,658, up nearly three times from 5,576 in the 1989 school year. Along with the increase of people with a doctorate, the number of post-doctorates working as part-time lecturers rose sixfold from 15,689 in 1989 to 93,145 in 2016.
Source: https://www.japantimes.co.jp/