Over the decade from 1997 to 2007 companies involved in providing payroll services saw the market for those services increase greatly. The number of establishments offering these services in 1997 was 2,709 and they employed 316,425 people. In 2007 there were 4,842 establishments employing 549,594 people.

Geographic reference: United States
Year: 1997 and 2007
Market size: $14.1 billion and $28.7 billion respectively
Source: “2007 Economic Census: Sector 54: Professional, Scientific, and Technical Services,” December 4, 2009, available online here as well as the “1997 Economic Census” data on the same industry.
Original source: U.S. Bureau of the Census