Mo. Rev. Stat. § 87.207
The following allowances due under the provisions of sections 87.120 to 87.371 of any member who retired from service shall be increased annually, as approved by the board of trustees beginning with the first increase in the October following his or her retirement and subsequent increases in each October thereafter, at the rates designated:
(1) With a retirement service allowance or ordinary disability allowance:
(L. 1969 p. 163 § 1, A.L. 1973 H.B. 591, A.L. 1983 H.B. 694 & 171, A.L. 2002 H.B. 1455 merged with S.B. 1107)
Effective 7-11-02 (H.B. 1455); 8-28-02 (S.B. 1107)