The series comes from the 'Current Employment Statistics (Establishment Survey)'
The source code is: CES6056100001
Source: US. Bureau of Labor Statistics
Release: Employment Situation
US. Bureau of Labor Statistics, All Employees: Professional and Business Services: Administrative and Support Services [CES6056100001], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/CES6056100001/, August 30, 2015.