Contained in the report, Health, United States, 2013, from the Centers for Disease Control and Prevention's National Center for Health Statistics, is the percentage of Medicare enrollees who are enrolled in Managed care. This information is provided by state.

You can find two lists on healthsprocket which contain information from this report on this topic; States with Highest Percentage of Medicare Enrollees in Managed Care and States with Lowest Percentage of Medicare Enrollees in Managed Care.

You can find the percentages for all states in the June DataMap from MCOL. This map and accompanying data is available to MCOL Premium Members. If you aren't a member yet consider signing up.