Tenn. Code § 8-3438
Effective July 1, 1949, there shall be paid into the accumulation fund, by the employer, on account of each member for each payroll period, an amount equal to such percentage of the compensation for current service of all members as may be determined on the basis of the actuarial evaluation set forth in §§ 8-3427, 8-3428, to be known as the employer's "current service" contribution and an additional amount equal to a percentage as may be determined, of the compensation for prior services of those members having prior service credits to be known as the employer's "prior service" contribution. In addition, each employer other than the state shall pay a pro rata share of the cost of the administration of the retirement system, based upon the payroll of the employees. Such payments shall be made by the employer at the same time as the employee's contribution is forwarded to the state treasurer. The rate per cent of such contribution shall be fixed by the board on the basis of the liabilities of the retirement system as shown by actuarial valuation. During the period over which the prior service contribution is payable the current service contribution rate shall be the uniform and constant percentage of the earned compensation of the average new entrant which if contributed on the basis of his compensation throughout his entire period of active service would be sufficient to provide for the payment of any benefit payable from the employers' contributions on his account. After the prior service contribution has ceased to be payable, the current service contribution rate shall be the rate per centum of the earned compensation of all members obtained by deducting from the present value of benefits payable from employers' contributions the amount of the funds in hand in the accumulation fund and dividing the remainder by one per cent (1%) of the present value of the prospective future salaries of all members. Until changed by the board the prior service contributions rate shall be four and eight one-hundredths per cent (4.08%).
T.C.A. § 8-3438