This HHS report analyzes Medical Expenditure Panel Survey (MEPS), finding that 32 percent of working age adults and their families had a health insurance coverage gap for at least one month in 2006 and 2007.

From the report:

Among all individuals who lost coverage, 85 percent were uninsured for at least one month, while only 13 percent gained individual market coverage for at least one month. The increased likelihood of becoming uninsured rather than obtaining individual market coverage is indicative of the high costs and inadequate coverage available in the individual market. In fact, a recent study found that almost 75 percent of individuals looking for coverage on the individual market never bought a plan. Sixty one percent of those who did not purchase the insurance cited premium cost as the primary reason.

Full report: Insurance Insecurity: Losing Employer-Sponsored Insurance Coverage (PDF | 569.57 KB)

U.S. Department of Health and Human Services. Agency for Healthcare Research and Quality. (2009). Insurance insecurity: families are losing employer-sponsored insurance coverage. Montz, H. and Seshamani, M.