California Code, Education Code - EDC § 26507

(a) The board may adjust the mandatory employer contribution rate specified under Section 26503 for a fixed period of plan years when it has determined based upon the recommendation of the actuary, that increased contributions are required.  The adjustment shall not exceed one-fourth of one percent for any plan year.  The mandatory employer contribution rate as adjusted shall not exceed 4.25 percent of salary in any plan year for each participant employed by the employer, except as provided in subdivision (b).

(b) The adjustment to the employer contribution rate specified in subdivision (a) shall be applied to the employer contribution rate specified in a collective bargaining agreement pursuant to Section 26504 and in effect on the first day of the plan year in which the adjustment to the employer contribution rate takes effect.

(c) The adjusted employer contribution rate shall become effective no earlier than the first day of the plan year immediately following adoption by the board.