The series comes from the 'Current Population Survey (Household Survey)'
The source code is: LNS13008516
Source: US. Bureau of Labor Statistics
Release: Employment Situation
US. Bureau of Labor Statistics, Number of Civilians Unemployed for 15 Weeks & Over [UEMP15OV], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/UEMP15OV/, June 3, 2015.