What a RAF score is
A RAF score turns a patient's profile into one number. The average Medicare beneficiary is normalized to about 1.0. A patient at 2.0 is expected to cost about twice the average, and one at 0.6 well below it. Plans and ACOs track the average RAF across their whole population.
The score is additive. It starts with demographic coefficients for age, sex, Medicaid eligibility, and whether the patient lives in the community or an institution. Then it adds a coefficient for each documented HCC, applying hierarchies so only the most severe condition in a family counts. Some disease combinations add interaction terms.
In Medicare Advantage, a plan's payment for a member is roughly a base rate multiplied by the member's RAF score, with further adjustments. In ACOs, RAF scores adjust the spending benchmark. In both, a missed annual visit can quietly lower the score, because undocumented conditions drop out of the next year's calculation.