About 20.6 million workers usually worked part time in 2000, most for noneconomic reasons.
Of these part-time workers, only 1.9 million worked part time for economic reasons, such as slack work or business conditions.
Among the remaining part-timers, about 6.2 million worked part time because they were in school or training—this was the most common reason for working part time. The next most common reason was "other family or personal obligations."
These data are a product of the Current Population Survey. Part time work is defined as working less than 35 hours per week. Additional information on part-time workers in 2000 can be found in Table 20 of the January 2001 Employment and Earnings.
Bureau of Labor Statistics, U.S. Department of Labor, The Economics Daily, Reasons for working part time at https://www.bls.gov/opub/ted/2001/mar/wk3/art03.htm (visited September 29, 2022).