The series comes from the 'Current Employment Statistics (Establishment Survey)'
The source code is: CES6054000001
Source: US. Bureau of Labor Statistics
Release: Employment Situation
US. Bureau of Labor Statistics, All Employees: Professional and Business Services: Professional and Technical Services [CES6054000001], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/CES6054000001/, September 2, 2015.