Where Medicare Advantage is most popular

States in the Midwest, South and West have the highest proportions of Medicare members enrolled in Medicare Advantage. Some states have more than 40% of their Medicare population in the taxpayer-subsidized private plans.

The big picture: Roughly a third of all Medicare enrollees are in MA, a program that has garnered bipartisan support despite its shortcomings, and some Wall Street estimates think MA will be the majority option by 2021.

By the numbers: More than 22 million seniors and people with disabilities have a Medicare Advantage plan, according to February 2019 enrollment data from the Centers for Medicare & Medicaid Services. The map highlights enrollment data from 2017, when there were 19.2 million MA enrollees.

• The state with the highest proportion of private Medicare plan enrollees (57.3%) is Minnesota, although many people are enrolled in "Medicare cost" plans that function as a hybrid between MA and traditional Medicare.
• MA is the choice of at least 40% of all Medicare enrollees in 6 other states (California, Florida, Hawaii, Oregon, Pennsylvania and Rhode Island).
• MA is far less popular in states with sparse populations, like Alaska, Vermont and Wyoming.

Between the lines: States with high concentrations of MA enrollees also have dominant systems of hospitals and doctors that sell MA plans.

• Many MA members in Pennsylvania buy plans from Highmark, Geisinger and UPMC, while Kaiser Permanente has a strong grip of the market along the West Coast.

What to watch: Health insurance companies will always aggressively pursue areas where there are a lot of seniors, like Florida and California, but the distribution shows there are pockets of the Midwest and Northeast that could be their next targets.