KENNEBUNK, ME – Between September 2008 and September 2009 the nation's top eight health insurance plans saw membership decline by 1.7 million.

Those losses are continuing in both the fully-insured and administrative services only (ASO) segments, according to Mark Farrah Associates, a Kennebunk, Maine-based provider of market data and intelligence solutions. The recession and high unemployment are being blamed for the losses.

Health plan membership decreased by 1.3 percent, from 133.2 million in 2008 to 131.5 million for 2009. ASO enrollment decreased 1.1 percent and risk enrollment declined 1.6 percent for these plans.

The eight leading companies reported a combined loss of 860,000 members between the second and third quarters of 2009, with ASO enrollment declining 0.4 percent and risk enrollment declining 0.9 percent for the period.

The Health Care Services Corporation, which includes Blue Cross and Blue Shield plans in Illinois, New Mexico, Oklahoma and Texas, and Humana were the only organizations among the top eight plans to see enrollment gains in the third quarter. Humana was also among the few plans that saw year-to-date profit margin improvement when compared to 2008.

The top eight U.S. health insurers are: Aetna, CIGNA, HCSC, Health Net, Humana, Kaiser Permanente, UnitedHealth Group and WellPoint. They cover nearly 60 percent of the total insured population in the nation. Membership data, financial statistics and observations are from the January 2010 Health Insurer Insights series.