Section 40 ILCS 5/11-150 - Mortality tables and interest rates(a) Any single life annuity fixed or granted to any employee who was a participant on or before January 1, 1952, or any reversionary or single life annuity, fixed for or granted to a wife or widow shall be computed, in the case of the employee as of his attained age when the annuity is fixed or granted, and in the case of the wife or widow, as of employee's age and that of his wife or widow on the date her annuity is fixed or granted, provided that if the wife or widow is older than 5 years the junior of her husband her age shall be assumed 5 years less than his. The American Experience Table of Mortality with interest at 4% per annum shall be used for the computation of the annuity values in this paragraph.(b) Until August 1, 1983, any single life annuity fixed or granted to any employee who becomes a participant for the first time after January 1, 1952, or any reversionary or single life annuity, fixed or granted to the wife or widow shall be computed, in the case of the employee as of his attained age when the annuity is fixed or granted, and in the case of the wife or widow her age shall be taken as 4 years younger than her actual age, or 4 years younger than the age of her husband, whichever will produce the lower age, as of the date the employee's or the wife's or widow's annuity is fixed or granted. The Combined Annuity Mortality Table for Male Lives with interest at 3 per cent per annum shall be used for the computation of the single life employee annuity values in this paragraph. Such table shall also be used for the computation of single life widow annuity values and for the computation of the reversionary annuities specified in this paragraph with the female life taken as 4 years less than the male life. On or after August 1, 1983, any single life annuity fixed or granted to any employee who becomes a participant for the first time after January 1, 1952, or any reversionary or single life annuity, fixed or granted to a wife or widow shall be computed, in the case of an employee as of his attained age when the annuity is fixed or granted, and in the case of the wife or widow her age shall be taken as the lower of her actual age or the age of her husband as of the date the employee's or wife's or widow's annuity is fixed or granted. The Combined Annuity Mortality Table for Male Lives with interest at 3% per annum shall be used for the computation of the single life employee and widow annuity values in this paragraph. Such table shall also be used for the computation of the reversionary annuity values specified in this paragraph with the employee life taken as 4 years less than the male life and the spouse life taken as the male life.
(c) All sums credited to any employee for annuity purposes when he withdraws from service before age 55 shall be improved with interest at the effective rate thereafter while he is not in service and has not entered upon annuity until he attains age 65.(d) The amount of widow's annuity or widow's prior service annuity which shall be fixed for the wife of an employee who is alive shall be calculated as a reversionary annuity derived from the total accumulated sum to the employee's credit for widow's annuity and widow's prior service annuity on the date the annuity is fixed.