Healthcare experts widely expected the Affordable Care Act to hobble Medicare Advantage, the government-funded private health plans that millions of seniors have chosen as an alternative to original Medicare.
To pay for expanding coverage to the uninsured, the 2010 law cut billions of dollars in federal payments to the plans. Government budget analysts predicted that would lead to a sharp drop in enrollment as insurers reduced benefits, exited states or left the business altogether.
But the dire projections proved wrong.
Since 2010, enrollment in Medicare Advantage has doubled to more than 20 million enrollees, growing from a quarter of Medicare beneficiaries to more than a third.
"The Affordable Care Act did not kill Medicare Advantage, and the program looks poised to continue to grow quite rapidly," said Bill Frack, managing director with L.E.K. Consulting, which advises health companies.
And as beneficiaries get set to shop for plans during open enrollment — which runs from Monday through Dec. 7 — they will find a greater choice of insurers.
Fourteen new companies have begun selling Medicare Advantage plans for 2019, several more than a typical year, according to a report out Monday from the Kaiser Family Foundation. (KHN is an editorially independent part of the foundation.)
Overall, Medicare beneficiaries can choose from about 3,700 plans for 2019, or 600 more than this year, according to the federal government's Centers for Medicare & Medicaid Services.
CMS expects Medicare Advantage enrollment to jump to nearly 23 million people in 2019, a 12 percent increase. Enrollees shopping for new plans this fall will likely find lower or no premiums and improved benefits, CMS officials say.

With about 10,000 baby boomers aging into Medicare range each day, the general view of the insurance industry, said Robert Berenson, a Medicare expert with the nonpartisan Urban Institute, "is that their future is Medicare and it's crazy not to pursue Medicare enrollees more actively."
Bright Health, Clover Health and Devoted Health, all for-profit companies, began offering Medicare Advantage plans for 2018 or will do so for 2019.
Mutual of Omaha, a company owned by its policyholders, is also moving into Medicare Advantage for the first time in two decades, providing plans in San Antonio and Cincinnati.
Some nonprofit hospitals are offering Medicare plans for the first time too, such as the BayCare Health system in the Tampa, Fla., area.
While Medicare beneficiaries in most counties have a choice of several plans, enrollment for years had been consolidated into several for-profit companies, primarily UnitedHealthcare, Humana and Aetna, which have accumulated just under half the national enrollment.
These insurance giants are also expanding into new markets for next year. Humana in 2019 will offer its Medicare HMO in 97 new counties in 14 states. UnitedHealthcare is moving into 130 new counties in 13 states, including for the first time Minnesota, its headquarters for the past four decades.