53 Pa. Stat. § 881.105
As soon as may be after the passage of this act, the actuary shall make an investigation of the mortality, service and salary experience of municipal employes, municipal firemen and municipal police as he shall deem necessary, for the purpose of determining upon tentative tables and municipal contributions. On the basis of such investigation and recommendation, the board shall adopt such tentative tables and certify such tentative rates for the purpose of giving municipalities and municipal employes, municipal firemen and municipal police estimates of the cost involved in electing to join the retirement system established by this act. The actuary shall make subsequent investigations at least once every five years in order to enable the board to change such tables when necessary.
53 P.S. § 881.105