White Mountains Insurance Group
Builds and supports insurance, reinsurance, and financial-services businesses.
$2,135.41
After-hours close+0.46 (+0.02%)
At close$2,134.95(+0.35%)
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Breakdown13F · Form 4
Institutions 320.89%Insiders 2.40%
A 13F quarter can total more than the shares outstanding — sub-advisers file the same block twice, and a filer's own share count can be a quarter stale. No split is drawn from it.
Shares outstanding 2.48M · Float 2.37M · 95.6% free float
Institutions13F, as of Jun 30, 2026
358 holders · 7.95M shares · 40 new positions · 137 increased · 145 reduced · 50 closed
| Holder | Shares | % outstanding | Chg q/q | Filed |
|---|---|---|---|---|
| Dimensional Fund Advisors LP | 159.0K | 6.42% | +2.3K | Aug 11, 2026 |
| Neuberger Berman Group LLC | 119.1K | 4.81% | −5.6K | Aug 13, 2026 |
| BlackRock, Inc. | 117.9K | 4.76% | +4.5K | Aug 7, 2026 |
| River Road Asset Management, LLC | 115.9K | 4.68% | −4.6K | Jul 17, 2026 |
| Vanguard Portfolio Management LLC | 112.0K | 4.52% | −3.6K | Aug 13, 2026 |
| Vanguard Capital Management LLC | 107.5K | 4.34% | −1.7K | Aug 13, 2026 |
| Fuller & Thaler Asset Management, Inc. | 101.9K | 4.11% | −2.7K | Aug 12, 2026 |
| Cooke & Bieler LP | 85.1K | 3.44% | −19.7K | Jul 30, 2026 |
Beneficial owners13D/G · 5% or more, as filed
| Holder | % of class | Shares | Form | Filed |
|---|---|---|---|---|
| Vanguard Capital Management | 5.18% | 128.0K | 13G | Apr 30, 2026 ↗ |
InsidersForm 4
| Insider | Role | Shares | % outstanding | Filed |
|---|---|---|---|---|
| Robert Lawrence Seelig | officer: EVP & General Counsel | 17.9K | 0.72% | Mar 20, 2026 |
| George Manning Rountree | director, officer: Chief Executive Officer | 13.8K | 0.56% | Dec 22, 2025 |
| Reid Tarlton Campbell | director | 10.6K | 0.43% | May 22, 2026 |
| Weston M. Hicks | director | 2.9K | 0.12% | May 22, 2026 |
| Michaela Hildreth | officer: MD & Chief Accounting Officer | 2.5K | 0.10% | Jan 5, 2026 |
| David Allen Tanner | director | 2.0K | 0.08% | May 22, 2026 |
| Mary C. Choksi | director | 2.0K | 0.08% | May 22, 2026 |
| Philip A. Gelston | director | 1.7K | 0.07% | May 22, 2026 |
| Liam P. Caffrey | officer: Chief Executive Officer | 1.7K | 0.07% | Jan 2, 2026 |
| Margaret Dillon | director | 1.1K | 0.04% | May 22, 2026 |
2 ten-percent owners hold 296.7K shares by Form 4, outside the officers-and-directors figure above · 21 people have not refiled in the last 18 months (440.8K shares), so they are not in the figure above
Latest trades
| Date | Insider | Type | Shares | Avg price | Owned after |
|---|---|---|---|---|---|
| Dec 19, 2025 | George Manning Rountreedirector, officer: Chief Executive Officer | Sale | 5,000 | $2,050.00 | 13,809 |
| Dec 19, 2025 | Reid Tarlton Campbelldirector | Sale · 2 lots | 10,000 | $2,050.00 | 10,440 |
| Dec 16, 2025 | Philip A. Gelstondirector | Sale | 165 | $2,048.51 | 1,568 |
CongressHouse and Senate disclosures
| Member | Type | Amount | Owner | Traded | Disclosed |
|---|---|---|---|---|---|
| Rep. Michael McCaul · TX10 | Sale | $1,001 – $15,000 | Spouse | Jun 18, 2026 | Jul 13, 2026 ↗ |