Cal. INS § 1234

The maximum rate for each policy shall be determined at regular intervals at least once every 12 months, but not more frequently than once in any three-month period. At the intervals specified in the policy: (1) The rate being charged may be increased whenever the increase as determined under subdivision (b) of Section 1232 would increase that rate by one-half of 1 percent or more per annum. (2) The rate being charged shall be reduced whenever the reduction as determined under subdivision (b) of Section 1232 would decrease that rate by one-half of 1 percent or more per annum.