The series comes from the 'Current Population Survey (Household Survey)'
The source code is: LNU01300000
Source: US. Bureau of Labor Statistics
Release: Employment Situation
US. Bureau of Labor Statistics, Civilian Labor Force Participation Rate [LNU01300000], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/LNU01300000/, July 6, 2015.
FRED BlogDon't be deceived by seasonality