White Mountains Insurance Group, Ltd. (WTM) Ownership
WTM ownership summary
as of October 18, 2026- Institutions
- 96.3% of shares outstanding
- Insiders
- 3.22% of shares outstanding
- Shares outstanding
- 2.4M
- Float
- 2.3M shares available to trade
- Short interest
- 6.04% 140K shares short
- Days to cover
- 6.85 short interest up 6.0% vs prior month
- Institutions 96.30%
- Insiders 3.22%
- Other investors 0.48%
WTM top institutional holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Dimensional Fund Advisors, Inc. | 6.66% | 159K | $343.4M | +2,336 (+1.5%) | June 30, 2026 |
| 2 | Neuberger Berman Group LLC | 4.99% | 119K | $257.4M | −5,574 (−4.5%) | June 30, 2026 |
| 3 | BlackRock Inc | 4.94% | 118K | $254.6M | +4,543 (+4.0%) | June 30, 2026 |
| 4 | River Road Asset Management, LLC | 4.86% | 116K | $250.3M | −4,639 (−3.8%) | June 30, 2026 |
| 5 | Vanguard Portfolio Management, LLC | 4.69% | 112K | $241.9M | −3,584 (−3.1%) | June 30, 2026 |
| 6 | Vanguard Capital Management, LLC | 4.50% | 107K | $232.2M | −1,678 (−1.5%) | June 30, 2026 |
| 7 | Fuller & Thaler Asset Management Inc | 4.27% | 102K | $220.1M | −2,669 (−2.6%) | June 30, 2026 |
| 8 | Cooke & Bieler LP | 3.57% | 85K | $183.9M | −19,737 (−18.8%) | June 30, 2026 |
| 9 | Wallace Capital Management, INC. | 3.30% | 79K | $170.2M | −1,552 (−1.9%) | March 31, 2026 |
| 10 | Fiduciary Management, Inc. of Milwaukee | 2.79% | 67K | $143.8M | −18,516 (−21.8%) | June 30, 2026 |
| 11 | Gendell Jeffrey L | 2.48% | 59K | $128.0M | +21,429 (+56.7%) | June 30, 2026 |
| 12 | Boston Partners Global Investors, Inc | 2.33% | 56K | $120.0M | −1,890 (−3.3%) | June 30, 2026 |
| 13 | London Company of Virginia | 2.26% | 54K | $116.7M | −3,106 (−5.4%) | June 30, 2026 |
| 14 | State Street Corp | 2.11% | 50K | $108.6M | +1,099 (+2.2%) | June 30, 2026 |
| 15 | Geode Capital Management, LLC | 2.07% | 49K | $106.7M | +7,293 (+17.3%) | June 30, 2026 |
| 16 | Morgan Stanley - Brokerage Accounts | 1.96% | 47K | $101.2M | −12,429 (−21.0%) | June 30, 2026 |
| 17 | Reinhart Mahoney Capital Management Inc | 1.84% | 44K | $95.0M | −521 (−1.2%) | September 30, 2026 |
| 18 | T. Rowe Price Investment Management,Inc. | 1.43% | 34K | $74.0M | −7,276 (−17.5%) | June 30, 2026 |
| 19 | Lord, Abbett & Co LLC | 1.38% | 33K | $70.9M | −281 (−0.8%) | June 30, 2026 |
| 20 | American Century Companies Inc | 1.30% | 31K | $67.2M | +22,800 (+274.4%) | June 30, 2026 |
Value at the latest close. Change = shares bought or sold in the latest quarterly filing (13F). In the top 20, 6 holders added 60K shares and 14 cut 83K.
WTM top mutual fund and ETF holders
20 largest| # | Holder | % of shares | Shares | Value | Change | Reported |
|---|---|---|---|---|---|---|
| 1 | Undiscovered Managers Behavioral Val L | 3.33% | 80K | $171.9M | −1,500 (−1.9%) | August 31, 2026 |
| 2 | Vanguard MStar Total Stk Mkt Idx Invest | 3.13% | 75K | $161.5M | −68 (−0.1%) | August 31, 2026 |
| 3 | Neuberger Genesis Inv | 2.88% | 69K | $148.3M | +480 (+0.7%) | September 30, 2026 |
| 4 | Vanguard Small Cap Index | 2.14% | 51K | $110.2M | −3,162 (−5.8%) | September 30, 2026 |
| 5 | Vanguard Selected Value Inv | 1.46% | 35K | $75.5M | −4,312 (−11.0%) | June 30, 2026 |
| 6 | Avantis US Small Cap Value ETF | 1.46% | 35K | $75.4M | +72 (+0.2%) | September 30, 2026 |
| 7 | DFA US Small Cap Value I | 1.40% | 33K | $72.0M | — | August 31, 2026 |
| 8 | Vanguard MStar Small Cap Value Index | 1.39% | 33K | $71.8M | −1,165 (−3.4%) | September 30, 2026 |
| 9 | FMI Common Stock Investor | 1.38% | 33K | $71.3M | −7,000 (−17.5%) | June 30, 2026 |
| 10 | Robeco BP US Premium Equities IH € | 1.30% | 31K | $66.9M | +490 (+1.6%) | August 31, 2026 |
| 11 | AMG River Road Small Cap Value N | 0.87% | 21K | $44.8M | — | September 30, 2026 |
| 12 | DFA US Targeted Value I | 0.84% | 20K | $43.3M | — | August 31, 2026 |
| 13 | Dimensional US Targeted Value ETF | 0.73% | 18K | $37.8M | +5 (+0.0%) | September 30, 2026 |
| 14 | Spiltan Globalfond Investmentbolag | 0.67% | 16K | $34.6M | — | September 30, 2026 |
| 15 | DFA US Small Cap I | 0.67% | 16K | $34.6M | — | August 31, 2026 |
| 16 | Longleaf Partners Small-Cap | 0.64% | 15K | $32.9M | — | June 30, 2026 |
| 17 | Strategic Advisers U.S. Total Stock | 0.57% | 14K | $29.5M | — | August 31, 2026 |
| 18 | Dimensional US Small Cap Value ETF | 0.56% | 13K | $29.0M | +4 (+0.0%) | September 24, 2026 |
| 19 | Allspring Special Small Cap Value A | 0.56% | 13K | $28.8M | −83 (−0.6%) | September 30, 2026 |
| 20 | JNL Multi-Manager Small Cap Value I | 0.54% | 13K | $27.7M | −7,281 (−36.2%) | June 30, 2026 |
Funds report holdings monthly or quarterly; dates differ by fund.
WTM insider transactions
latest 1| Date | Name | Transaction | Price | Shares | Value |
|---|---|---|---|---|---|
| 2025-12-16 | Philip A Gelston | Sell | $2,048.51 | 165 | $338,004 |
Reported trades by company officers, directors and other filers (including disclosures by members of Congress where EODHD lists them). "—" where the filing gives no share count.
WTM shares outstanding
Year-end shares outstanding, adjusted for splits.
Who owns WTM
Institutional investors own 96.3% of White Mountains Insurance's shares and insiders 3.22%. The largest holder is Dimensional Fund Advisors, Inc. with 6.66% of the shares (159K), as of June 30, 2026. Among the top 20 institutions, 6 added shares and 14 reduced their stake in the latest filings. Short interest is 6.04% of the float, or 6.85 days of average trading volume. The share count fell 57.4% since 2014.
Related: WTM key metrics, WTM dividend history. See the WTM stock overview for the latest quote and news.
WTM ownership FAQ
Who owns the most White Mountains Insurance stock?
The largest shareholders of White Mountains Insurance are Dimensional Fund Advisors, Inc. (6.66%), Neuberger Berman Group LLC (4.99%), BlackRock Inc (4.94%), River Road Asset Management, LLC (4.86%), Vanguard Portfolio Management, LLC (4.69%).
What percentage of White Mountains Insurance is owned by institutions?
Institutions hold 96.3% of White Mountains Insurance's shares outstanding; insiders hold 3.22%.
Which funds own White Mountains Insurance?
The largest fund holders of White Mountains Insurance are Undiscovered Managers Behavioral Val L (3.33%), Vanguard MStar Total Stk Mkt Idx Invest (3.13%), Neuberger Genesis Inv (2.88%), Vanguard Small Cap Index (2.14%), Vanguard Selected Value Inv (1.46%).
What is White Mountains Insurance's short interest?
140K shares of White Mountains Insurance were sold short, 6.04% of the float; at the average daily volume it would take 6.85 days to cover.
Are insiders buying or selling White Mountains Insurance?
Of the latest 1 reported insider transactions in White Mountains Insurance (since December 16, 2025), 0 were purchases and 1 were sales.
How many shares of White Mountains Insurance are outstanding?
White Mountains Insurance has 2.4M shares outstanding, of which 2.3M are in the public float.