For service annuity: July 1, 1919 to July 13, 1927, inclusive, 8% of salary; July 14, 1927 to July 20, 1947, inclusive, 11% of salary; July 21, 1947 to August 3, 1961, inclusive, 10% of salary.
For widow's service annuity: July 1, 1919 to July 13, 1927, inclusive, 2% of salary; July 14, 1927 to August 3, 1961, inclusive, 2 3/4% of salary.
In determining the amounts to be contributed by an employer on behalf of an employee for service annuity and widow's service annuity in conformity with the percentage prescribed for such annuities, the contributions to be made by the employee during any fiscal year shall be accumulated at regular interest to the end of such year, and the employer shall make his contributions plus such interest, with additional regular interest between the end of such fiscal year and the dates when contributions by the employer are made.
40 ILCS 5/12-152