I increased my position in White Mountains Insurance (WTM) from 4,7% to about 9,4% of my portfolio. White Mountains Insurance is a specialty insurance holding company with a stellar track record of capital discipline, long-term value creation, and underwriting profitability. While I didn’t publish a full write-up at the time of my initial investment, my thesis remains rooted in WTM’s unique positioning as an long-term compounder that prioritizes economic value over accounting optics.
Over the past two decades, WTM has compounded adjusted book value (ABV) at 9.2% annually — not as remarkable as Berkshire Hathaway but still impressive, given its conservatively managed balance sheet, opportunistic capital allocation, and shareholder-aligned management approach. ABV provides a more accurate view of intrinsic value than GAAP book value (BV) because it adjusts for economic reality — most notably by adding net unearned premium reserves from HG Global (a wholly-owned reinsurer). This metric is also preffered by company’s own management, since better it reflects economics of the business.
One likely factor behind the recent price weakness is the announced CEO transition. However, this change appears well-planned and low-risk: current CFO Liam Caffrey will take over from Manning Rountree in early 2026, ensuring continuity. Importantly, WTM’s success has never relied on a single central figure (unlike Berkshire Hathaway); rather, it reflects a deep culture of rational capital allocators, disciplined underwriters, and decentralized operators — a structure designed for longevity.
With broader equity markets richly valued and my idea pipeline currently thin, WTM stands out as a high-conviction idea as it trades at almost 8% discount to adjusted book value; offering a ~17% implied rate of return based on conservative assumptions (that compounded annual growth rate will average at 8% in the long-term future, which is lower than the historical figure of 9.2%). While this purchase raises my total insurance sector exposure to around 25% of the portfolio (including Fairfax and Berkshire), I’m comfortable with the concentration given the quality, diversification, and risk profile of the underlying businesses.