For further information, please refer to the US Census Bureau's Annual Services release, online at http://www.census.gov/services/.
Source: US. Bureau of the Census
Release: Annual Services Survey
US. Bureau of the Census, Defined Contribution Plans for Internet Publishing and Broadcasting and Web Search Portals, All Establishments, Employer Firms (DISCONTINUED SERIES) [EXPDCPEF51913ALLEST], retrieved from FRED, Federal Reserve Bank of St. Louis https://research.stlouisfed.org/fred2/series/EXPDCPEF51913ALLEST/, September 1, 2015.