(a) General. For agreement periods beginning on January 1, 2025, and in subsequent years, CMS calculates the population adjustment to the historical benchmark.

(b) Calculation of the population adjustment. To calculate the adjustment described in paragraph (a) of this section, CMS does all of the following:

(1) Calculates the weighted average of the ACO's third benchmark year (BY3) national per capita expenditure amounts across the following populations of beneficiaries, where the weights are the ACO's BY3 proportion of assigned beneficiaries for that enrollment type:

(i) ESRD.

(ii) Disabled.

(iii) Aged/dual eligible Medicare and Medicaid beneficiaries.

(iv) Aged/non-dual eligible Medicare and Medicaid beneficiaries.

(2) Calculates a scaler as the difference between 5 percent of the national per capita expenditure amount, expressed as single value as calculated in paragraph (b)(1) of this section, and the higher of: the regional adjustment, expressed as a single value as described in § 425.656(d); the per capita prior savings adjustment determined in § 425.658(c); or no adjustment, in the case where the regional adjustment is negative and the ACO is not eligible for the prior savings adjustment under § 425.658(b)(3)(i).

(3) Determines the ACO's eligibility for the population adjustment based on the proportion of the ACO's assigned beneficiaries for the performance year who are enrolled in the Medicare Part D low-income subsidy (LIS) or dually eligible for Medicare and Medicaid. An ACO is only eligible for the population adjustment if this proportion is greater than or equal to 15 percent. An ACO with a proportion less than 15 percent is ineligible to receive the population adjustment.

(4) Calculates the population adjustment. If the ACO is eligible for the population adjustment as determined in paragraph (b)(3) of this section, the adjustment is equal to the product of the scaler calculated in paragraph (b)(2) of this section and the proportion of the ACO's assigned beneficiaries for the performance year who are enrolled in the Medicare Part D LIS or dually eligible for Medicare and Medicaid.

(c) Applicability of the population adjustment. CMS compares the population adjustment determined in paragraph (b)(4) of this section with the regional adjustment, expressed as a single value as described in § 425.656(d), and the per capita prior savings adjustment determined in § 425.658(c), if any, to determine the adjustment, if any, that will be applied to the ACO's benchmark in accordance with § 425.652(a)(8)(ii).