Humana

Humana commands 20%+ of the Medicare Advantage market with 5.8 million members, outperforming #4 Aetna by 2.3 million members in that critical senior segment. Despite generating $116 billion in revenue—over 30% less than UnitedHealth—the Louisville-based insurer's focused government-sponsored plan strategy delivers a 94% Medicare retention rate. Its administrative cost ratio of 8.2% is 2.1 percentage points lower than the industry average, enabling competitive premium pricing for seniors.