In addition to the increase in allowance authorized and granted pursuant to provisions of Section 21313, and notwithstanding the limitation on those increases imposed by this article, effective January 1, 1980, or the date this section becomes applicable to the contracting agency, the monthly allowance paid with respect to a state or local member, other than a school member, who retired or died prior to January 1, 1975, shall be increased by the percentage set forth opposite the year of retirement or death in the following schedule:
Period during which retirement or death occurred
Percentage
12 months ending December 31, 1967
1.51
12 months ending December 31, 1968
1.26
12 months ending December 31, 1969
1.86
12 months ending December 31, 1970
2.55
6 months ending June 30, 1971
1.91
6 months ending December 31, 1971
7.05
12 months ending December 31, 1972
6.76
12 months ending December 31, 1973
4.45
6 months ending June 30, 1974
0.47
6 months ending December 31, 1974
1.31
The percentage shall be applied to the allowance payable on January 1, 1980, or the date this section becomes applicable to the contracting agency, and the allowance
as so increased shall be paid for time on and after the date and until the first day of April immediately following the date of application. The base allowance shall be the allowance as increased under this section. The base year for annual adjustments of allowances increased by this section shall be the calendar year preceding the year of increase if the increase date is after April 1st of any calendar year, and the second calendar year preceding the year of increase if the increase date is on or before April 1st of any calendar year.
This section shall not apply to any contracting agency unless the agency elected to be subject to the provisions of this section in its contract with the board on or before December 31, 2001.