The Centers for Medicare and Medicaid Services uses a star rating system to evaluate Medicare Advantage plans and Medicare Part D plans. Plans can receive from one star (poor) to five stars (excellent), and the ratings are based on numerous measures, including factors such as customer service, how easy it is for enrollees to receive care, how well the plan does at improving or maintaining members’ physical and mental health, and how quickly the plan handles appeals — among many others (see Tables 9, 10, and 11).
Star ratings are assigned at the contract level, rather than the plan level. Most contracts have numerous plans, but all plans under a given contract receive the same star rating. Some contracts do not receive star ratings, either because sufficient data are not available, or because the contract is too new.
For 2020, the average Medicare Advantage plan with integrated Part D coverage (MA-PD) received 4.16 stars (average is weighted by enrollment). And the average stand-alone Part D plan received 3.5 stars. As of 2019, nearly three-quarters of all Medicare Advantage enrollees were in plans that received at least four stars.
If there’s a 5-star plan available in a given area, Medicare beneficiaries in that area have an opportunity to switch to that plan throughout most of the year (from December 8 through November 30). But there are very few Medicare Advantage or Part D contracts that receive five stars — as of 2020, only 23 contracts have five stars. Most are Medicare Advantage plans (two are Part D plans, but they’re offered as employer-sponsored group coverage).