On June 22, KFF released a report examining 2010 data on Medicare Advantage (MA) plan enrollment patterns and trends.  As of March 2010, the report found that 11.1 million individuals, or one-quarter of all Medicare beneficiaries, were enrolled in MA plans.  In March 2009, 10.5 million beneficiaries were enrolled in MA plans.  The report notes that, although most Medicare beneficiaries have numerous MA plans available to them, enrollment is concentrated among a small number of insurers in almost every state. 

From the report:

In general, our analysis finds a small number of firms dominate Medicare Advantage enrollment both nationally and in most states; for example, in 14 states and the District of Columbia, a single firm accounts for more than half of all Medicare Advantage enrollment. The average Medicare beneficiary in 2010 has 33 Medicare Advantage plans available in their area, with the average enrollee paying a monthly premium of $44 per month, a 22 percent increase since 2009 ($36 per month). The health reform legislation of 2010 gradually phases down payments to Medicare Advantage plans over time which is expected to ultimately affect plan participation, enrollment, premiums and extra benefits. Yet, even with these changes, Medicare Advantage plans can be expected to remain an important option for many beneficiaries.

Full report: Medicare Advantage 2010 Data Spotlight (PDF | 342KB)

Kaiser Family Foundation. (2010). Medicare Advantage 2010 data spotlight: plan enrollment patterns and trends. Gold, M., Phelps, D., Jacobson, G. and Neuman, T.