Tenn. Code § 17-516
On the basis of such actuarial assumptions as the board may adopt, the actuary appointed by the board shall make at least biennially a valuation of the assets and liabilities of this retirement system. Based on the results of such valuations, the board shall make recommendations to the general assembly for such changes in this chapter as the board deems desirable for the purpose of assuring that the retirement system will continue to be properly designed and actuarially sound.
In 1967 and each five (5) years thereafter the board shall direct the actuary to investigate actual experience underlying the actuarial assumptions and recommend to the board for adoption new sets of assumptions in line with the results of his investigation.
T.C.A. § 17-516