ADOPTING RATES AND TABLES

(a) The board of trustees shall adopt rates and tables that the board considers necessary for the retirement system after considering the results of the actuary's investigation of the mortality and service experience of the system's members and annuitants. In adopting rates and tables, the board of trustees shall adopt a discount rate that is not less than five percent in developing an annuity purchase rate. (b) Based on recommendations of the actuary, the board of trustees shall adopt rates and tables necessary to determine the supplemental death benefits contribution rates for each municipality participating in the supplemental death benefits fund. (c) The board of trustees, after consultation with the actuary, by rule or by funding policy adopted by the board of trustees, may: (1) set open or closed amortization periods not to exceed 30 years; (2) change the period for amortizing a municipality's unfunded actuarial accrued liabilities from an open period to a closed period or from a closed period to an open period; (3) decrease or increase the amortization period, provided the amortization period may not exceed 30 years; and (4) set different amortization periods for unfunded actuarial accrued liabilities arising from different types of events giving rise to liabilities and ladder the amortization of the liabilities. (d) In this section: (1) "Annuity purchase rate" means the present value factor used to convert reserves to a monthly annuity based on the post-retirement discount rate assumption and the life expectancy of the retiree or beneficiary or both the retiree and the beneficiary at retirement under the selected form of payment. (2) "Discount rate" means the interest rate used in determining the present value of future cash flows.