42 C.F.R. § 512.426
(b) Metric included in the efficiency domain. For each PY, CMS assesses the IOTA participant on the following metric:
(1) Organ-offer acceptance rate ratio. For each PY, CMS calculates the organ-offer acceptance rate ratio by dividing the number of kidneys the IOTA participant accepted by the risk-adjusted number of expected organ-offer acceptances using SRTR's methodology as described in equation 1 to paragraph (b)(1) introductory text of this section.
Equation 1 to Paragraph (b)(1) Introductory Text—Organ Offer Acceptance Rate Ratio

(i) CMS uses both of the following:
(ii) CMS includes all of the following kidney offers when calculating the organ-offer acceptance rate ratio for the IOTA participant:
(iii) CMS excludes the following kidney offers when calculating the organ-offer acceptance rate:
(c) Efficiency domain scoring. For each PY, CMS awards the IOTA participant 0 to 20 points for its performance in the efficiency domain.
(2) Scoring for organ offer acceptance rate ratio. CMS calculates the IOTA participant's achievement score, as described in paragraph (c)(2)(i) of this section, and improvement score, as described under paragraph (c)(2)(ii) of this section, for the organ offer acceptance rate ratio, compares the IOTA participant's achievement score and improvement score and awards to the IOTA participant the points that correspond to the higher score.
(i) Achievement scoring. CMS calculates the IOTA participant's achievement score based on the IOTA participant's performance on organ offer acceptance rate ratio relative to national ranking, including all eligible kidney transplant hospitals, using the scoring methodology described in table 1 to paragraph (c)(1)(i) of this section.
Table 1 to Paragraph (c)(1)(i)—IOTA Model Organ Offer Acceptance Rate Ratio Achievement Scoring

(ii) Improvement scoring. CMS compares the IOTA participant's organ offer acceptance rate ratio during the PY, calculated as described under paragraph (c)(1)(i) of this section, to the IOTA participant's improvement benchmark rate, calculated as described under paragraph (c)(1)(ii)(A) of this section.
(B) Improvement score calculation. For each PY, CMS uses the following methodology to determine each IOTA participant's improvement score on the organ offer acceptance rate ratio:
(1) If the IOTA participant's organ-offer acceptance rate ratio is greater than or equal to the improvement benchmark rate, CMS awards the IOTA participant 15 points in the efficiency domain.
(2) If the IOTA participant's organ offer acceptance rate ratio is equal to or less than the IOTA participant's organ-offer acceptance rate ratio in the third baseline year for that respective PY, CMS awards the IOTA participant 0 points in the efficiency domain.
(3) If the IOTA participant's organ offer acceptance rate ratio is greater than the IOTA participant's organ-offer acceptance rate ratio in the third baseline year for that respective PY but less than the improvement benchmark rate, CMS uses the following equation:
Equation 2 to Paragraph (c)(2)(ii)(B)(3)—IOTA Model Organ Offer Acceptance Rate Ratio Improvement Scoring Equation
