Wyo. Stat. Ann. § 15-5-421

Each employer shall make monthly contributions to the account in an amount equal to the percentage contribution rate multiplied by the salaries paid to members of the account. The contribution rate, expressed as a percentage, shall be based on the results of actuarial valuations made at least every three (3) years. The city's contribution rate shall be comprised of the normal cost plus the payment required to amortize the actuarial liability over a period of thirty (30) years calculated on the basis of an amortization policy approved by the board.