White Mountains Insurance (WTM) concentration risks

The company's concentration profile is centered on two high-share dependency exposures within its operating subsidiaries, with a third, more limited single-name relationship disclosed at a lower level. Within the Distinguished business, the three largest carriers during the year ended December 31, 2025 accounted for approximately 61% of placed business, a large share by disclosed size and a dependency character. Carrier concentration of this magnitude means that the withdrawal, capacity reduction, or ratings downgrade of any of those three relationships could materially impair Distinguished's ability to place risk on behalf of its clients. Separately, HG Re is dependent on BAM's ability to write municipal bond insurance policies, a high-share dependency by disclosed size. This is a structural constraint on HG Re's business: since HG Re is only licensed to provide reinsurance to BAM, its revenue and loss experience are entirely a function of BAM's underwriting activity and financial condition. Any regulatory, credit, or strategic development at BAM flows directly through to HG Re. Within Distinguished, the single largest carrier accounted for approximately 22% of placed business during the same period, a limited share by disclosed size at the individual-name level within that subsidiary. That single name is the most immediately visible point of counterparty dependency within the broader group of carriers. Taken together, the carrier concentration at Distinguished and the exclusive BAM relationship at HG Re are the two most material disclosed exposures in the profile.

For the engine’s reasoning on WTM’s current verdict — including which dimensions drove the score — see the per-dimension breakdown.

Concentration counts reflect items disclosed in each peer’s most recent 10-K; disclosed-size classification uses TrendMatrix’s internal 10-K extraction taxonomy.