Mo. Rev. Stat. § 86.330

After each annual valuation, the actuary engaged by the board to make the valuation required by sections 86.200 to 86.366, shall determine the normal contribution rate. The normal contribution rate shall be the rate percent of the earnable compensation of all members obtained by deducting from the total liabilities of the retirement system the amount of the assets in hand to the credit of the retirement system and the present value of expected future member contributions and dividing the remainder by one percent of the present value of the prospective future compensation of all members as computed on the basis of mortality and service tables and interest assumptions adopted by the board of trustees.