Cal. Government Code § 31588.1

There is hereby established in the County Employees’ Retirement System a deferred yield adjustment account which shall be increased by the sale or disposition of any debt securities at less than book value and shall be decreased by the sale or disposition of debt securities at more than book value. At the end of each year, a portion of the balance of this account shall be offset against the investment income for that year. The annual portion of the balance to be offset shall be proportional to the reciprocal of the average remaining life of the bonds sold. The amount of this account shall be included in any accounting or actuarial computations or listing of assets. In any year in which the gains on the sales of debt securities exceed the discounts realized on the sales of such securities, the excess shall be used to reduce the balance of the account. This section shall not be operative in any county until such time as the board shall, by resolution adopted by majority vote, make the provisions of this section applicable in such county.