Effective July 1, 1968, the monthly benefits, inclusive of the supplemental allowances payable under the provisions of Sections 9-1-1910, 9-1-1920 and 9-1-1930, for persons who commenced receiving benefits from the System prior to July 1, 1967 and subsequent to June 30, 1966 shall be increased by five percent, and such monthly benefits to persons who commence receiving benefits in each fiscal year thereafter through the fiscal year ending June 30, 1970, shall be increased by five percent provided that there is sufficient investment income in excess of the valuation interest assumption to fund such increases or a proportionate part thereof on a lifetime basis, as determined by the actuary.
The minimum increase pursuant to this section, inclusive of the increase in the supplemental allowances, shall be five dollars per month. However, if an optional benefit has been elected, the minimum shall be reduced actuarially as determined by the Board, and shall be applicable to the retired member or his designated beneficiary under the option elected.