UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 APRIL 10, 2003 Date of Report (Date of earliest event reported) WHITE MOUNTAINS INSURANCE GROUP, LTD. (Exact name of registrant as specified in its charter) BERMUDA 1-8993 94-2708455 (State or other jurisdiction of (Commission (I.R.S. Employer incorporation or organization) file number) Identification No.) 80 SOUTH MAIN STREET, HANOVER, NEW HAMPSHIRE 03755 (Address of principal executive offices) (603) 640-2200 (Registrant's telephone number, including area code) ITEM 5. OTHER EVENTS. On April 10, 2003, White Mountains Insurance Group, Ltd. made available on its website a reconciliation of non-GAAP financial measures (as defined in Regulation G of the Securities and Exchange Commission) contained in its 2002 Management Report and 2002 Annual Report on Form 10-K. The reconciliation, which is attached hereto as Exhibit 99 (a), is incorporated herein by reference. ITEM 7. FINANCIAL STATEMENTS AND EXHIBITS. (c) Exhibits. The following exhibit is filed herewith: EXHIBIT INDEX 99 (a) Reconciliation of non-GAAP financial measures. SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned thereunto duly authorized. WHITE MOUNTAINS INSURANCE GROUP, LTD. DATED: APRIL 10, 2003 BY: /s/ J. BRIAN PALMER ------------------------------------- J. BRIAN PALMER CHIEF ACCOUNTING OFFICER
EXHIBIT 99 (A) ONEBEACON A GAAP combined ratio is calculated by adding (i) the ratio of incurred loss and loss adjustment expenses ("LAE") to earned premiums (the "loss and LAE ratio") and (ii) the ratio of commissions, premium taxes and other underwriting expenses recognized under GAAP, including general and administrative expenses, to earned premiums (the "expense ratio"). OneBeacon's trade ratio is a modified statutory combined ratio. A statutory combined ratio is calculated by adding (i) the loss and LAE ratio and (ii) the ratio of commissions, premium taxes and other underwriting expenses recognized under statutory accounting principles, including general and administrative expenses, to written premiums (the "expense ratio"). In calculating OneBeacon's trade ratio, the statutory expense ratio is modified by dividing certain other underwriting expenses not directly associated with producing premiums, including general and administrative expenses, by earned premiums rather than written premiums. OneBeacon believes that the trade ratio is the best measure of the underwriting performance of its business because it links the elements of the expense ratio relating to the cost of producing the business to written premiums and the elements relating to the costs of operating the business to earned premiums. The GAAP combined ratio primarily differs from the trade ratio in the expense ratio calculation. The differences between the GAAP expense ratio and the trade expense ratio include differences between statutory accounting principles and GAAP. For example, acquisition costs (principally commissions and premium taxes) are expensed when the associated premiums are written for statutory purposes but are deferred and amortized ratably as the associated premiums are earned for GAAP purposes. Additionally, as mentioned above, the GAAP expense ratio measures all expense recognized to earned premiums whereas the trade expense ratio measures acquisition costs to written premiums. The following tables reconcile OneBeacon's trade ratios to GAAP combined ratios for each respective underwriting sub-segment and in total for the twelve months ended December 31, 2002 and provide a comparative reconciliation of trade ratios to GAAP combined ratios for the twelve months ended December 31, 2001.