Sec. 21. (a) The pension portion (plus postretirement increases to the pension portion) provided by employer contributions of the monthly benefit payable after June 30, 1990, to a member or a survivor or beneficiary of a member who retired or was disabled:
(1) before July 2, 1971, shall be increased by three percent (3%);
(2) after July 1, 1971, and before July 2, 1976, shall be increased by two percent (2%); and
(3) after July 1, 1976, and before July 2, 1983, shall be increased by one percent (1%).
(b) In addition to the increase specified in subsection (a), the pension portion (plus postretirement increases to the pension portion), provided by employer contributions of the monthly benefit payable after June 30, 1990, to a member or a survivor or beneficiary of a member, who retired or was disabled before July 2, 1988, shall be increased by two percent (2%).