The series comes from the 'Current Population Survey (Household Survey)'
The source code is: LNU03032225
Source: US. Bureau of Labor Statistics
Release: Employment Situation
US. Bureau of Labor Statistics, Unemployment Level: Installation, Maintenance, and Repair Occupations [LNU03032225], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/LNU03032225/, July 1, 2015.