MA enrollment increased nearly 30% in 2 years. Your Medicare managed care headaches probably won't be going away any time soon. The Department of Health & Human Ser-vices expects enrollment in Medicare Advantage plans to increase by 11 percent next year, HHS says in a release. Since 2010, MA enrollment has grown 28 percent, the department notes. HHS expects the average MA premium in 2013 to increase by $1.47 from last year, coming to $32.59. Open enrollment for MA health and drug plans begins Oct. 15 and ends Dec. 7.