(1) The monthly retirement allowance payable to a retirant or beneficiary on or after September 30, 1976, who was on the rolls for April 1, 1978, is supplemented as follows:

Effective Date of Retirement Percent Supplemented
10-1-76 10-1-77
July 1, 1975 to June 30, 1976 1 1
July 1, 1974 to June 30, 1975 2 2
July 1, 1973 to June 30, 1974 3 3
July 1, 1972 to June 30, 1973 4 4
July 1, 1971 to June 30, 1972 5 5
July 1, 1970 to June 30, 1971 6 6
July 1, 1969 to June 30, 1970 7 7
July 1, 1968 to June 30, 1969 8 8
Before July 1, 1968 8 8

(2) The supplement to the retirement allowance provided by this section shall be paid only during those fiscal years for which an appropriation is made which is sufficient to cover the additional payments likely to be made.