At least half of new Medicare advantage enrollees had switched from traditional Medicare during 2006-11.

With ongoing interest in rising Medicare Advantage enrollment, we examined whether the growth in enrollment between 2006 and 2011 was mainly due to new beneficiaries choosing Medicare Advantage when they first become eligible for Medicare. We also examined the extent to which beneficiaries in traditional Medicare switched to Medicare Advantage, and vice versa. We found that 22 percent of new Medicare beneficiaries elected Medicare Advantage over traditional Medicare in 2011; they accounted for 48 percent of new Medicare Advantage enrollees that year. People ages 65-69 switched from traditional Medicare to Medicare Advantage at higher-than-average rates. Dual eligibles (people eligible for both Medicare and Medicaid) and beneficiaries younger than age sixty-five with disabilities disenrolled from Medicare Advantage at higher-than-average rates. On average, in each year of the study period we found that fewer than 5 percent of traditional Medicare beneficiaries switched to Medicare Advantage, and a similar percentage of Medicare Advantage enrollees switched to traditional Medicare. These results suggest that initial coverage decisions have long-lasting effects.