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) 1995 1994 1994 1993 1992 (1) 1991 1990 ------- ------- ------- ------- --------- ------- ------- Income from continuing operations before provision for income taxes $ 318.1 $ 279.7 $ 537.6 $ 479.1 $ 290.5 $ 331.5 $ 325.2 Add back fixed charges: Interest on indebtedness 27.0 22.1 46.4 42.3 41.9 40.7 44.4 Interest on ESOP 2.7 3.0 5.9 6.5 6.9 7.2 7.4 Portion of rents representative of interest factor 12.0 15.8 28.7 26.1 19.2 15.4 13.2 ------- ------- ------- ------- --------- ------- ------- INCOME AS ADJUSTED $ 359.8 $ 320.6 $ 618.6 $ 554.0 $ 358.5 $ 394.8 $ 390.2 ======= ======= ======= ======= ========= ======= ======= FIXED CHARGES: Interest on indebtedness: Aon Corporation and consolidated subsidiaries $ 27.0 $ 22.1 $ 46.4 $ 42.3 $ 41.9 $ 40.7 $ 43.9 Unconsolidated subsidiaries - - - - - - 0.5 ------- ------- ------- ------- ---------- ------- ------- INTEREST 27.0 22.1 46.4 42.3 41.9 40.7 44.4 Interest on ESOP 2.7 3.0 5.9 6.5 6.9 7.2 7.4 Portion of rents representative of interest factor 12.0 15.8 28.7 26.1 19.2 15.4 13.2 ------- ------- ------- ------- ---------- ------- ------- TOTAL FIXED CHARGES $ 41.7 $ 40.9 $ 81.0 $ 74.9 $ 68.0 $ 63.3 $ 65.0 ======= ======= ======= ======= ========== ======= ======= RATIO OF EARNINGS TO FIXED CHARGES 8.6 7.8 7.6 7.4 5.3 6.2 6.0 ======= ======= ======= ======= ========== ======= ======= (1) Income from continuing operations before provision for income taxes excludes the cumulative effect of changes in accounting principles. -21-