(

a) An actuarial valuation shall be made within one year after the date on which any system established under this

chapter becomes effective, and thereafter at intervals not to exceed three years. The valuation shall be conducted under the supervision of an actuary and shall cover the mortality, service, and compensation experience of the members and beneficiaries, and shall evaluate the assets and liabilities of the retirement fund.

Upon the basis of the investigation, valuation, and recommendation of the actuary, the board shall, at least days prior to the beginning of the succeeding fiscal year, recommend to the board of supervisors the changes in the rates of interest, in the rates of contributions of members, and in county and district appropriations as are necessary. With respect to the rates of interest to be credited to members and to the county or district, the board may, in its sound discretion, recommend a rate that is higher or lower than the interest assumption rate established by the actuarial survey.

No adjustment shall be included in the new rates for time prior to the effective date of the revision. (b)

(1) Upon the basis of the investigation, valuation, and recommendation of the actuary, the board shall, at least days prior to the beginning of the succeeding fiscal year, recommend to the governing body of a district within the county system that is not governed by the board of supervisors the changes in the rates of contributions of district members and in district appropriations as are necessary.

(2) This subdivision shall not be operative in any county until the board of supervisors, by resolution adopted by majority vote, makes the provision applicable in that county.