A look at the Medicare Advantage landscape for 2018

A third of Medicare Advantage enrollees are in plans with narrow networks, though MA plans on average include about half of physicians in a given county, according to new research. 

Meanwhile, the Centers for Medicare & Medicaid Services has announced that premiums in such plans will decrease for 2018. 

The Kaiser Family Foundation examined data on 391 MA plans offered by 55 insurers in 20 counties and found that, on average, the plans covered 46% of physicians in each county. However, 35% of people were enrolled in narrow-network plans that covered 30% or fewer of physicians in the counties where they live. 

More MA enrollees were in "medium" networks that covered between 30%-70% of physicians in their counties, and 22% were in broad-network MA plans that covered 70% of physicians or more. 

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The breadth of provider networks is the major trade-off for most consumers as they chose between MA plans and traditional Medicare. Enrollees in MA plans with broader networks often paid higher premiums, according to KFF. 

However, CMS has announced that premiums for 2018 Medicare Advantage plans are set to decrease as enrollment in MA is projected to reach an all-time high.  

CMS estimated that the average monthly MA premium will decrease by $1.91, a drop of about 6% from 2017. Seventy-seven percent of MA enrollees who choose to remain in their current plan for 2018 will see the same or decreased premiums. 

CMS projects that 20.4 million people will enroll in MA for 2018, an increase of 9% over 2017. More than a third (34%) of Medicare beneficiaries are enrolled in MA.

RELATED: As seniors get sticker, they're more likely to drop Medicare Advantage plans 

"The success of Medicare Advantage and the prescription drug program demonstrates what a strong and transparent health market can do—increase quality while lowering costs," CMS Administrator Seema Verma said. 

HealthPocket, a website that allows consumers to comparison shop for health insurance, found that 30% of MA plans for 2018 will have no premium at all, though enrollees will still pay the premiums for Medicare Part B. That is a slight increase from 29% in 2017. 

The lowest monthly MA premiums for 2018 on average are in Florida, according to HealthPocket, at $17.06. The highest premiums were recorded in North Dakota at $116.25, more than six times higher.