Postretirement Increase. The monthly benefit payable on and after July 1, 1980, to a member, or a survivor or beneficiary of a member, who retired or was disabled:
The increase specified in this section shall be based upon the date of the member's initial retirement or disability. This section does not apply to benefits payable in a lump sum. The increases provided by this section are in addition to any other increase provided by law.
IC 5-10.2-5-8