(a) Employees who retired on service retirement annuity prior to July 1, 1970, who were at least 55 years of age at date of retirement shall be entitled to receive a supplementary annuity under this section.
(b) The Board may set cost-of-living increases for annuitants and pensioners and determine when the annuity should be paid on the basis of the most recent actuarial valuation, the Consumer Price Index, or other economic studies or evaluations that the Board may determine are relevant.
(c) In the case of a member on retirement who is receiving, in addition to the retirement annuity from this system, a special pension grant from the government not paid by the retirement system, the following conditions shall govern:
(d) In the case of members on disability retirement, the increase shall be 1 percent of the disability annuity times the number of full years that he has been in receipt of such annuity prior to his attainment of age 60, and 1 ½ percent of the disability annuity for each year after attainment of such age.
(e) The supplementary annuity payable under this section shall be charged to a retired employee’s supplementary annuity reserve. This reserve shall be credited with investment earnings above 4 percent per annum, as established and earned by the system in each fiscal year to fund these annuities.