A record number of people are enrolled in private Medicare Advantage plans despite payment changes, according to new analysis.

The Kaiser Family Foundation said that 14.4 million Medicare beneficiaries are enrolled in those plans this year, up nearly 10 percent from 2012 and 30 percent since 2010.

Enrollment has grown significantly since enactment of Medicare’s prescription drug benefit and comes despite the fact that the average number of plans available to enrollees nationwide fell from a high of 48 plans in 2009 to 20 each of the last two years.

Researchers, though, cautioned that the Patient Protection and Affordable Care Act could disrupt the market as “payment reductions have not been fully phased in and quality-based bonus payments have partly off-set the payment reductions.”

Over the next few years, it is possible there will be some shakeout in the market as payment reductions are implemented and benchmarks move closer to spending for traditional Medicare,” researchers wrote in their report.

“Ultimately, to remain viable, some plans either will have to become more efficient or modify the extra benefits they provide to their enrollees.”

The law cut plans’ reimbursements by about $156 billion to bring them more in line with traditional Medicare.

Researchers also said that while about 28 percent of Medicare beneficiaries nationally are now enrolled in Medicare Advantage plans, the share varies greatly by state—ranging from 49 percent in Minnesota to less than 4 percent in Iowa and Alaska.

They also said national Medicare Advantage enrollment tends to be concentrated among a small number of organizations, with five firms (and affiliates) accounting for two-thirds of enrollment.