The normal rate of contribution shall be such as will provide an average annuity at age 50 equal to one two-hundredth of the final compensation of safety members according to the table adopted by the board of supervisors for each year's service rendered after entering the system.
This section shall become operative in any county on the first day of the calendar month after the board of supervisors adopts a resolution making it operative in the county.
Ca. Gov. Code § 31639.5