The series comes from the 'Current Population Survey (Household Survey)'
The source code is: LNU03032226
Source: US. Bureau of Labor Statistics
Release: Employment Situation
US. Bureau of Labor Statistics, Unemployment Level: Production, Transportation and Material Moving Occupations [LNU03032226], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/LNU03032226/, July 8, 2015.