According to a 2007 GAO analysis of BLS and CPS data, "while the share of large employers offering health benefits remained fairly constant between 2001 and 2006 at about 98 percent, the share of small employers (with 3-199 employees) offering them dropped from 68 percent to 60 percent." (p. 17)
U. S. Government Accountability Office. (2007). Employer-sponsored health and retirement benefits. Washington, DC: U.S. Government Accountability Office. Retrieved from http://purl.access.gpo.gov/GPO/LPS82868
This report is based on data from three private-sector surveys of employer-sponsored health benefits and two federal surveys that address workforce characteristics and benefits costs and participation rates, including the Current Population Survey (CPS), which is designed and administered jointly by the Bureau of the Census and Bureau of Labor Statistics (BLS), and the Mercer National Survey of Employer-Sponsored Health Plans; Mercer's 2005 database contains information from 2,122 large (over 500) and small (under 500) employers who sponsor health plans.