40 ILCS 5/14-109

(a) Beginning January 1, 1987, any person who is receiving a monthly retirement annuity under this Article which, after inclusion of (1) all one-time and automatic annual increases to which the person is entitled, (2) any supplemental annuity payable under Section 14-115, and (3) any amount deducted under Section 14-113 to provide a reversionary annuity, is less than the minimum monthly retirement benefit amount specified in subsection (b) of this Section, shall be entitled to a monthly supplemental payment equal to the difference. (b) For purposes of the calculation in subsection (a): (1) Until January 1, 1997, the minimum monthly retirement benefit amount is the sum of $15 for each year of service as a noncovered employee, plus $7.50 for each year of service as a covered employee, up to a maximum of 30 years of service. (2) Beginning January 1, 1997, the minimum monthly retirement benefit amount is the sum of $25 for each year of service as a noncovered employee, plus $15 for each year of service as a covered employee, up to a maximum of 30 years of service. (c) This Section applies to all persons receiving a retirement annuity under this Article, without regard to whether or not employment terminated prior to the effective date of this amendatory Act of 1996.