40 ILCS 5/12-122
"Salary": (a) The annual salary of any employee whose salary is on a yearly basis; (b) 12 times the amount of the salary per month of an employee whose salary is on a monthly basis; (c) 52 times the amount of the salary per week of an employee whose salary is on a weekly basis; (d) 260 times the amount of the salary per day of an employee whose salary is on a daily basis or 2,080 times the amount of the salary per hour of an employee whose salary is on an hourly basis. The number of days or hours in excess of the maximum prescribed by the employer shall not be considered; (e) the maximum annual salary when arranged on a yearly basis to be considered for contributions and benefits for the various purposes of this Article for the periods specified shall be as follows: July 1, 1919 to June 30, 1921, inclusive, $2,500; July 1, 1921 to July 20, 1947, inclusive, $3,000; July 21, 1947, to June 30, 1951, inclusive, $4,800; July 1, 1951 to June 30, 1957, inclusive, $6,000; July 1, 1957 and thereafter, no maximum limitation; (f) the maximum annual salary where arranged on other than a yearly basis to be considered for contributions and benefits for the various purposes of this Article for the periods prior to the effective date of the formulas specified in paragraph (b), (c) or (d) of this section, shall be computed in accordance with the applicable law in force during such periods.
Salary for part-time employment in positions of a seasonal or part-time character shall be computed in accordance with the foregoing standards as the same may be applicable for the respective periods of employment under rules established by the board.
40 ILCS 5/12-122