According to the source, value added represents the sum of the costs-incurred and the incomes-earned in production, and consists of compensation of employees, taxes on production and imports, less subsidies, and gross operating surplus.
Source: US. Bureau of Economic Analysis
Release: Gross Domestic Product by Industry
US. Bureau of Economic Analysis, Contributions to Percent Change in Real GDP by Private Industries: Professional and Business Services: Professional, Scientific, and Technical Services [CPGDPPST], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/CPGDPPST/, October 7, 2015.