How Medicaid Is Financed

Every dollar of Medicaid spending is split between the federal government and a state. How that split works, the Federal Medical Assistance Percentage (FMAP), shapes both the program’s politics and the arithmetic of any value-based arrangement built on top of it.

The FMAP formula

The federal share “is based on a formula that provides higher reimbursement to states with lower per capita incomes relative to the national average.” Poorer states get a larger federal match; wealthier states get less. Two guardrails bound the result:

• A floor of 50 percent. No state pays more than half.
• A ceiling of 83 percent. No state pays less than 17 percent.

A separate, higher rate applies to the expansion population: for adults made newly eligible under the Affordable Care Act, the federal government pays 90 percent, phased down from 100 percent in the early years.

The open-ended match

The feature that matters most is easy to miss: the federal match is open-ended. The federal government pays its FMAP share of whatever a state actually spends on covered services, with no preset dollar cap. Spend more and the federal contribution rises automatically; spend less and it falls.

Worth remembering: the open-ended match is why Medicaid savings are shared savings. When a value-based program lowers Medicaid spending, both the state and the federal government keep a portion, in FMAP proportion. Neither captures the whole benefit, which shapes who is willing to invest.

Why the politics differ from Medicare

Medicare is federal money and federal savings. Medicaid is shared, and states cannot run deficits. That changes everything:

• A state weighing a value-based investment only keeps its FMAP share of any savings, so the business case is weaker than it looks.
• Medicaid competes inside the state budget with schools, roads, and pensions, so cost growth creates pressure that Medicare does not face the same way.
• Proposals to change the federal match (block grants, per-capita caps, altered FMAP) are perennial precisely because the open-ended structure is what makes the program grow.

Key takeaways

• FMAP sets the federal share by a per-capita-income formula, floored at 50 percent and capped at 83 percent.
• The expansion population carries a 90 percent federal match.
• The match is open-ended, so Medicaid savings are split between state and federal budgets, weakening any single actor’s incentive to invest.

Sources

• MACPAC, Medicaid 101: Financing (opens in a new tab)
• Congressional Research Service, Medicaid’s Federal Medical Assistance Percentage (FMAP), R43847 (opens in a new tab)