The Impact of the Affordable Care Act on Medicare Advantage Plan Availability and Enrollment


Address correspondence to Christopher C. Afendulis, Ph.D., Department of Health Care Policy, Harvard Medical School, 180 Longwood Avenue, Boston, MA 02115; e-mail:



To assess the impact of the Patient Protection and Affordable Care Act's (ACA) changes in Medicare Advantage (MA) payment rates on the availability of and enrollment in MA plans.

Data Sources

Secondary data on MA plan offerings, contract offerings, and enrollment by state and county, in 2010–2011.

Study Design

We estimated regression models of the change in the number of plans, the number of contracts, and enrollment as a function of quartiles of FFS spending and pre-ACA MA payment generosity. Counties in the lowest quartile of spending are treated most generously by the ACA.

Principal Findings

Relative to counties in the highest quartile of spending, the number of plans in counties in the first, second, and third quartiles rose by 12 percent, 7.6 percent, and 5.4 percent, respectively. Counties with more generous MA payment rates before the ACA lost significantly more plans. We did not find a similar impact on the change in contracts or enrollment.


The ACA-induced MA payment changes reduced the number of plan choices available for Medicare beneficiaries, but they have yet affected enrollment patterns.