(a) Subject to the provisions of paragraph (b) of this Section, the retirement annuity for any employee who withdraws from service on or after January 1, 1983 and before January 1, 1990, at age 60 or over, having at least 4 years of service, shall be 1.70% for each of the first 10 years of service; 2.00% for each of the next 10 years of service; 2.40% for each year of service in excess of 20 but not exceeding 30; and 2.80% for each year of service in excess of 30, with a pro-rated amount for service of less than a full year, based upon the highest average annual salary for any 4 consecutive years within the last 10 years of service immediately preceding the date of withdrawal, provided that: (1) if retirement of the employee occurs below age 60, such annuity shall be reduced 1/2 of 1% for each month or fraction thereof that the employee's age is less than 60, except that an employee retiring at age 55 or over but less than age 60, having at least 35 years of service, shall not be subject to the reduction in his retirement annuity because of retirement below age 60; (2) the annuity shall not exceed 75% of such average annual salary; (3) the actual salary shall be considered in the computation of this annuity. The retirement annuity for any employee who withdraws from service on or after January 1, 1990 and prior to December 31, 2003 at age 50 or over with at least 10 years of service, or at age 60 or over with at least 4 years of service, shall be 1.90% for each of the first 10 years of service, 2.20% for each of the next 10 years of service, 2.40% for each of the next 10 years of service, and 2.80% for each year of service in excess of 30, with a pro-rated amount for service of less than a full year, based upon the highest average annual salary for any 4 consecutive years within the last 10 years of service immediately preceding the date of withdrawal, provided that:
(1) if retirement of the employee occurs below age 60, such annuity shall be reduced 1/4 of 1% (1/2 of 1% in the case of withdrawal from service before January 1, 1991) for each month or fraction thereof that the employee's age is less than 60, except that an employee retiring at age 50 or over having at least 30 years of service shall not be subject to the reduction in retirement annuity because of retirement below age 60;(2) the annuity shall not exceed 80% of such average annual salary; and(3) the actual salary shall be considered in the computation of this annuity. An employee who withdraws from service on or after December 31, 2003, at age 50 or over with at least 10 years of service or at age 60 or over with at least 4 years of service, shall receive, in lieu of any other retirement annuity provided for in this Section, a retirement annuity calculated as follows: for each year of service immediately preceding the date of withdrawal, 2.40% of the highest average annual salary for any 4 consecutive years within the last 10 years of service immediately preceding the date of withdrawal, with a prorated amount for service of less than a full year, provided that:
(1) if retirement of the employee occurs below age 60, such annuity shall be reduced 1/4 of 1% for each month or fraction thereof that the employee's age is less than 60, except that an employee retiring at age 50 or over having at least 30 years of service shall not be subject to the reduction in retirement annuity because of retirement below age 60;(2) the annuity shall not exceed 80% of such average annual salary; and(3) the actual salary shall be considered in the computation of this annuity. Notwithstanding any other formula, the annuity for employees retiring on or after January 31, 2004 and on or before February 29, 2004 with at least 30 years of service shall be 80% of average annual salary for any 4 consecutive years within the last 10 years of service immediately preceding the date of withdrawal.