40 ILCS 5/6-145
Any annuity fixed for or granted to a present employee or future entrant who entered service prior to July 1, 1953, or to his widow, shall be computed according to the American Experience Table of Mortality. The rate of interest to be used for all purposes of this Article on account of such persons shall be 4% per annum.
Annuities for future entrants entering service after June 30, 1953, and for widows and persons having a right to annuities or benefits through such future entrants, shall be computed according to the Combined Annuity Mortality Table, rated back 4 years for female lives. The rate of interest for all purposes of this Article on account of such future entrants and their beneficiaries shall be 3% per annum.
All sums to the credit of a fireman for annuity purposes at the time he withdraws before age 50 shall be improved to his credit thereafter by interest while he is out of service and has not entered upon annuity until he attains age 57. Such interest shall be 4% per annum if he is a present employee or a future entrant who entered service prior to July 1, 1953, or 3% per annum if he is a future entrant who enters service after June 30, 1953. Any annuity fixed for or granted to such employees who entered service prior to July 1, 1953, and who have not re-entered the service prior to the time such annuity is fixed or granted, or any annuity fixed for or granted to a widow of any such employee shall be computed according to the American Experience Table of Mortality with interest at 4% per annum, and any annuity fixed for or granted to any such future entrant who entered service subsequent to June 30, 1953 or his widow shall be computed according to the Combined Annuity Mortality Table rated back 4 years for female lives and with interest at 3% per annum.
The amount of widow's annuity or widow's prior service annuity which shall be fixed for the wife of a fireman while he is alive shall be a reversionary annuity computed according to the applicable table of mortality.
40 ILCS 5/6-145