A survey of the number of workers by type of employment in Japan was started from 2000, and showed a considerable increase of part-time workers, which increased from 7.19 million in 2000 to 10.48 million in 2019, an increase of approximately 3.30 million workers.

[Reference] "Labor Force Special Survey" by the Ministry of Internal Affairs and Communications up to 2001 (every February)
"Labor Force Survey" by the Ministry of Internal Affairs and Communications since 2002 (average of January to March every year)