WHITE MOUNTAINS INSURANCE GROUP LTD (WTM) stock intrinsic value fair value estimate & owner earnings analysis

White Mountains is a Bermuda-based holding company that owns a collection of insurance and financial businesses rather than one operating company. The main pieces are Ark, a specialty property and casualty insurer and reinsurer; HG Global, which reinsures municipal bond insurance; Kudu, which buys revenue interests in asset and wealth management firms; Distinguished, a specialty insurance agency acquired in September 2025; and a pool of other holdings including a stake in MediaAlpha, an interest in insurance broker BroadStreet, and roughly a billion dollars of capital not yet put to work. Earnings belonging to common shareholders over the last decade ran $80, $146, negative $42, $130, $227, negative $89, $277, $199, $90 and $430 per share. Two of those ten years were outright losses, and the best year was driven almost entirely by an $816 million gain on selling the Bamboo agency, worth about $320 per share on its own. Because reported profit swings this violently, we leaned on book value per share as the anchor. It grew from roughly $696 at the end of 2015 to $2,188 at the end of 2025 and about $2,258 at mid-2026, close to 12 percent a year, while the share count fell by more than half as management repurchased stock, most recently at 92 percent of book value. Averaged across the decade the company earned about 11 percent on shareholders' equity, and that return on equity is what we projected forward. The bear case assumes a long stretch of only 7.5 percent returns as insurance pricing softens, private investment marks reverse and idle cash earns little, with capital handed back rather than reinvested, giving roughly $1,510 a share. The base case carries the historical 10.5 percent return forward and lands near $2,745. The bull case assumes 13 percent returns with continued profitable sales of businesses and gets to about $4,140. The balance sheet is strong, with $837 million of debt against $5.4 billion of common equity, so we did not layer any additional debt adjustment on top. Our confidence is moderate, around three in four: book value is a solid anchor, but a large share of it sits in privately valued assets and Ark carries hurricane exposure that can dent a year badly. We'd want to pay around $1,775, comfortably below book value, before buying. The company's cash flow statement is not meaningful for a business like this and was not used.