Illinois Statutes Chapter 40. Pensions § 5/16-112. Regular interest

(a) For computations based upon prior service credits, interest at the following rates compounded annually: For periods prior to July 1, 1947, 4% per year; for periods from July 1, 1947 through June 30, 1971, 3% per year; for periods from July 1, 1971 through June 30, 1977 at the rate of 4% per year; for periods from July 1, 1977 through June 30, 1981, 5% per year; for periods after June 30, 1981 through June 30, 2014, 6% per year.

(b) For computations based upon membership service credits, interest at the following rates, compounded annually: For periods prior to July 1, 1971, 3% per year; for periods from July 1, 1971 through June 30, 1977, 4% per year; for periods from July 1, 1977 through June 30, 1981, 5% per year; for periods after June 30, 1981 through June 30, 2014, 6% per year.

(c) For a fiscal year that begins on or after July 1, 2014, for all computations, the interest rate of 30-year United States Treasury bonds on July 1 of that given fiscal year, plus 75 basis points.