Medicare Advantage in Yellowstone County, Montana
14,653 people in Yellowstone County, Montana were enrolled in Medicare Advantage in October 2026, 38.4% of 38,206 eligible beneficiaries (+0.7 pts since October 2025). Humana Inc. is the largest parent organization with 63% of reported enrollment; 7 parent organizations have 11 or more members and the HHI is 4,456 (highly concentrated). HRSA classifies the county as partly rural. For 2027, 3,899 members here are in plans that terminate or leave the county, and Health Care Service Corporation, PacificSource leave. MA plans offered go from 22 to 12.
Parent organizations in Yellowstone County
| Parent organization | Members | Change since October 2025 | Share |
|---|---|---|---|
| Humana Inc. | 9,250 | +2,055 | 63.4% |
| UnitedHealth Group, Inc. | 2,439 | −1,038 | 16.7% |
| Health Care Service Corporation | 1,374 | −462 | 9.4% |
| PacificSource | 1,099 | +125 | 7.5% |
| CVS Health Corporation | 373 | +3 | 2.6% |
| Elevance Health, Inc. | 35 | +2 | 0.2% |
| California Physicians' Service | 11 | new | under 0.1% |
CMS suppresses county and contract counts of 10 or fewer; shares are of reported enrollment.
Value-based care alongside MA
In PY 2024, 13,630 beneficiaries in Yellowstone County were assigned to 85 Medicare Shared Savings Program ACOs, 82.2% of assignable Original Medicare beneficiaries. Together, roughly 89% of all Medicare beneficiaries in the county are in Medicare Advantage or an MSSP ACO. See the ACOs in the MSSP Explorer.