White Mountains Insurance Group, Ltd. (WTM) ownership: insiders 3% · institutions 82% · index and ETF funds 9% (13F 2026-03-31). Insider activity, 90 days: 0 sales, 0 open-market buys. 2 recent congressional STOCK Act disclosures. SEC EDGAR first-party data.
| Holder | Shares | Market Value | % Outstanding | Reported |
|---|---|---|---|---|
| Vanguard | 244160.00 | $536.41M | 9.9% | 2026-03-31 |
| Dimensional Fund Advisors | 156618.00 | $344.08M | 6.3% | 2026-03-31 |
| Neuberger Berman | 124715.00 | $273.99M | 5.0% | 2026-03-31 |
| River Road Asset Management, LLC | 120519.00 | $264.78M | 4.9% | 2026-03-31 |
| BlackRock | 113328.00 | $248.98M | 4.6% | 2026-03-31 |
| Cooke & Bieler LP | 104857.00 | $230.37M | 4.2% | 2026-03-31 |
| Fuller & Thaler Asset Management, Inc. | 104561.00 | $229.72M | 4.2% | 2026-03-31 |
| Fiduciary Management Inc | 85066.00 | $186.89M | 3.4% | 2026-03-31 |
| Insider | Transaction | Value | Date |
|---|---|---|---|
| Sell | null | 2026-08-31 | |
| Sell | null | 2026-08-26 | |
| Sell | null | 2026-05-21 | |
| Sell | null | 2026-05-21 | |
| Sell | null | 2026-05-21 | |
| Sell | null | 2026-05-21 | |
| Sell | null | 2026-05-21 | |
| Sell | null | 2026-05-21 |
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Institutional data from SEC Form 13F. Insider data from SEC Form 4. Congressional data from STOCK Act disclosures. Not personalized investment advice.