Exhibit 12(a) Aon CORPORATION AND CONSOLIDATED SUBSIDIARIES COMBINED WITH UNCONSOLIDATED SUBSIDIARIES COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES Six Months Ended June 30, Years Ended December 31, ----------------- ----------------------------------------------------- (millions except ratios) 1996 1995 1995 1994 1993 1992(1) 1991 ------ ------ ------ ------ ------ ------- ------- Income from continuing operations before provision for income taxes $ 246.9 $ 244.7 $ 458.0 $ 397.0 $ 331.6 $ 179.1 $ 242.4 Add back fixed charges: Interest on indebtedness 23.9 27.0 55.5 46.4 42.3 41.9 40.7 Interest on ESOP 2.4 2.7 5.3 5.9 6.5 6.9 7.2 Portion of rents representative of interest factor 13.4 12.0 21.4 28.7 26.1 19.2 15.4 ------ ------ ------ ------ ------ ------ ------ INCOME AS ADJUSTED $ 286.6 $ 286.4 $ 540.2 $ 478.0 $ 406.5 $ 247.1 $ 305.7 ====== ====== ====== ====== ====== ====== ====== FIXED CHARGES: Interest on indebtedness $ 23.9 $ 27.0 $ 55.5 $ 46.4 $ 42.3 $ 41.9 $ 40.7 Interest on ESOP 2.4 2.7 5.3 5.9 6.5 6.9 7.2 Portion of rents representative of interest factor 13.4 12.0 21.4 28.7 26.1 19.2 15.4 ------ ------ ------ ----- ----- ----- ----- TOTAL FIXED CHARGES $ 39.7 $ 41.7 $ 82.2 $ 81.0 $ 74.9 $ 68.0 $ 63.3 ====== ====== ====== ===== ===== ===== ===== RATIO OF EARNINGS TO FIXED CHARGES 7.2 6.9 6.6 5.9 5.4 3.6 4.8 ====== ====== ====== ===== ===== ===== ===== Ratio of earnings to fixed charges (2) 8.1 8.6 8.4 7.6 7.4 5.3 6.2 ====== ====== ====== ===== ===== ===== ===== (1) Income from continuing operations before provision for income taxes excludes the cumulative effect of changes in accounting principles. (2) The calculation of this ratio of earnings to fixed charges reflects the addition of the income from discontinued operations before the provision for income tax component for each period presented. 32