Medicare Advantage plans represent a sizable and growing segment of the Medicare program as well as important private plan alternatives to traditional Medicare. According to the latest statistics, enrollment in Medicare Advantage plans increased from 13% of the Medicare population, or 5.3 million individuals, in 2004 to almost 33%, or 19 million individuals, in 2017, and government payments to Medicare Advantage plans have increased from $77 billion to more than $200 billion per year over the same period. With these payments, Medicare Advantage plans are obligated to provide at least the same level of coverage as traditional Medicare. However, Medicare Advantage plans have significant flexibility to augment benefits, and many plans both add benefits (eg, vision and dental coverage) and lower cost sharing; these enhancements have proven to be popular to many beneficiaries. These additional benefits can also come with certain restrictions not present in traditional Medicare, such as more limited networks of clinicians or health care organizations and more referral requirements to see specialists.