Chapter 2 from its Databook on Employee Benefits, includes data on employer and individual spending on benefits and benefit payments to individuals.
The data, presented in aggregate of billions of dollars, uses the National Income and Product Accounts of the United States (NIPA) produced by the U.S. Department of Commerce, Bureau of Economic Analysis. Data is presented for each year 1948-2006, and there are three spread sheets in the chapter which present the data in 2006 dollars. All of the data is free to download, and available HERE
Chapter 5 in the Databook contains data on participation and expenditures on various government benefit related programs such as Social Security, Medicare, Medicaid, TANF, etc. The data is presented for 1940-2005 with a spread sheet that adjusts the expenditure amounts to 2005 dollars. In addition there is a table presenting data on the federal government’s revenue loss estimates due to employee benefit programs. Data is presented for 1975-2007 with a spread sheet that adjusts to 2006 dollars. That information is available HERE
The revenue source table provides data from 1975-2007 by year, and for all employee benefit categories over the years in one easy to use source.