Which superinvestors hold White Mountains Insurance Gp (WTM)?

Per the latest SEC 13F filings, 1 superinvestor hold White Mountains Insurance Gp (WTM): Mason Hawkins. Combined value held is about $35.5M, with Mason Hawkins the largest holder.

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White Mountains Insurance Gp

WTM

Held by 1 superinvestor.

Price$2132.74

Holders1

Total value$35.5M

SEC 10-K · fundamentals

Business quality

as of 2025-12-31

Valuation basis: trailing twelve months to 2026-06-30 — latest 10-K plus unaudited 10-Q filings.

Revenue growth: +66.8%
Net margin: 29.6%
ROE: 20.4%
FCF margin: —

Revenue $1.18B → $3.73B · 6y

What makes a business high quality

Valuation · value band

Valuation

This is a holding company whose balance sheet is led by an investment portfolio. Comparing consolidated earnings power against reproduction value says nothing here — a marketable portfolio reproduces at its own market price, so owning it is not a competitive barrier. No value range or moat verdict is shown; the asset floor below is a floor only.

Asset floor (per share): $1,746.39

SEC 13F · holders

Superinvestors Holding This Security

1 holder · $35.5M combined · this quarter +0 opened / -1 exited

This quarter1 trimmed1 exited

Holders 1 → 1 · last 8q

Investor	Value	Shares	Weight (prev→now)
Mason Hawkins	$35.5M	17,104	2.0% → 1.8% ▼

Mason Hawkins
Value$35.5MWeight (prev→now)2.0% → 1.8% ▼

Exited this quarter (1)

Ray Dalio

SEC 13F · notes

Written summary

White Mountains Insurance Gp (WTM) is held by 1 of the superinvestors tracked on Compounder, with a combined $35.5M in reported 13F value. The largest position belongs to Mason Hawkins, where it makes up 1.8% of the portfolio.

Over the latest quarter, 0 of the tracked filers opened a new position in WTM, 0 added to existing ones, 1 trimmed, and 1 sold out entirely.

Holder counts and values reflect the most recent SEC Form 13F filings, through the quarter ended 2026-06-30. Source: SEC EDGAR. A 13F shows only long US-listed positions and can lag the real portfolio by up to 45 days, so this is disclosed long ownership, not a complete picture.

How to read a 13F

SEC 13F · co-ownership

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Also on

Sources· SEC EDGAR 13F as of 2026-06-30 · filed 2026-08-14

Educational data only — not investment advice. 13F positions are self-reported and can lag up to 45 days.

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