Rule 112. The rate of interest for purposes of repayment of a refund, purchase of out-of-system public education service and other creditable service, and crediting individual member accounts shall be at such rate as the retirement board from time to time determines. For these purposes, the board may determine a rate of interest, hereafter referred to as the "board-determined rate of interest (BDRI)," which shall not exceed the assumed actuarial rate of return.
Mich. Admin. Code R. 38.1112