<Page> EXHIBIT 12(b) AON CORPORATION AND CONSOLIDATED SUBSIDIARIES COMBINED WITH UNCONSOLIDATED SUBSIDIARIES COMPUTATION OF RATIO OF EARNINGS TO COMBINED FIXED CHARGES AND PREFERRED STOCK DIVIDENDS <Table> <Caption> NINE MONTHS ENDED SEPTEMBER 30, YEARS ENDED DECEMBER 31, ---------------------------- ------------------------------------------------------ (millions except ratios) 2002 2001 (2) 2001 2000 1999 1998 1997 ----------- ---------------- ----------- ----------- ---------- ---------- ------- (RESTATED) Income before provision for income taxes and minority interest $ 504 $ 245 $ 309 $ 854 $ 635 $ 931 $ 542 ADD BACK FIXED CHARGES: Interest on indebtedness 91 98 127 140 105 87 70 Interest credited on investment-type insurance contracts 27 44 56 71 77 72 45 Interest on ESOP - - - - 1 2 3 Portion of rents representative of interest factor 38 39 57 54 49 51 44 ----------- ------------- ----------- ----------- ---------- ---------- -------- INCOME AS ADJUSTED $ 660 $ 426 $ 549 $ 1,119 $ 867 $ 1,143 $ 704 =========== ============= =========== =========== ========== ========== ======== FIXED CHARGES AND PREFERRED STOCK DIVIDENDS: Interest on indebtedness $ 91 $ 98 $ 127 $ 140 $ 105 $ 87 $ 70 Preferred stock dividends 52 52 70 70 70 70 82 ----------- ------------- ----------- ----------- ---------- ---------- -------- INTEREST AND DIVIDENDS 143 150 197 210 175 157 152 Interest credited on investment-type insurance contracts 27 44 56 71 77 72 45 Interest on ESOP - - - - 1 2 3 Portion of rents representative of interest factor 38 39 57 54 49 51 44 ----------- ------------- ----------- ----------- ---------- ---------- -------- TOTAL FIXED CHARGES AND PREFERRED STOCK DIVIDENDS $ 208 $ 233 $ 310 $ 335 $ 302 $ 282 $ 244 =========== ============= =========== =========== ========== ========== ======== RATIO OF EARNINGS TO COMBINED FIXED CHARGES AND PREFERRED STOCK DIVIDENDS (1) 3.2 1.8 1.8 3.3 2.9 4.1 2.9 =========== ============= =========== =========== ========== ========== ======== </Table> - --------------------- (1) Included in total fixed charges and preferred stock dividends are $49 million for the nine months ended September 30, 2002 and 2001, $66 million for the years ended December 31, 2001, 2000, 1999 and 1998, and $64 million for the year ended December 31, 1997, of pretax distributions on the 8.205% mandatorily redeemable preferred capital securities which are classified as "minority interest" on the condensed consolidated statements of income. (2) The computation of Ratio of Earnings to Combined Fixed Charges and Preferred Stock Dividends for nine months ended September 30, 2001 has been restated from what had previously been reported to include interest credited on investment-type insurance contracts.