The series comes from the 'Current Population Survey (Household Survey)'
The source code is: LNU04032224
Source: US. Bureau of Labor Statistics
Release: Employment Situation
US. Bureau of Labor Statistics, Unemployment Rate: Construction and Extraction Occupations [LNU04032224], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/LNU04032224/, September 5, 2015.