The series comes from the 'Current Population Survey (Household Survey)'
The source code is: LNU02032200
Source: US. Bureau of Labor Statistics
Release: Employment Situation
US. Bureau of Labor Statistics, Total At Work in Nonagricultural Industries, Worked 1 to 34 Hours, for Noneconomic Reasons, Usually Work Part Time [LNU02032200], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/LNU02032200/, July 5, 2015.