Enrollment in Medicare Advantage (MA) plans, measured either as an overall count or as a proportion of eligible Medicare beneficiaries continues to climb with one in three Medicare beneficiaries enrolled in an MA plan in March 2017. Among non-metropolitan enrollees, nearly one in four (23.5%) beneficiaries is enrolled in an MA plan. The majority of all MA enrollees are in Health Maintenance Organization (HMO) plans but that is largely driven by metropolitan enrollees. The majority of non-metropolitan MA enrollees are in preferred provider organization (PPO) plans, either local PPOs (38.5%) or regional PPOs (17.7%).