WTM Institutional Ownership & Shareholders
WHITE MTNS INS GROUP LTD (WTM) is currently held by 360 institutional investors tracked by InsiderSet, with a combined reported market value of approximately $4.60B based on the latest available SEC Form 13F filings for the quarter ended June 30, 2026.
Dimensional Fund Advisors Lp is currently the largest disclosed institutional shareholder of WTM tracked by InsiderSet, reporting ownership valued at approximately $329.58M in its June 30, 2026 SEC Form 13F filing. Based on current market prices and the latest disclosed share count, the position is now estimated to be worth approximately $360.82M, representing an estimated gain of +9.48% since the filing period.
The top 10 institutional shareholders tracked on this page collectively account for approximately 48% of the total disclosed WTM value among the investors covered in this analysis. Major shareholders include Dimensional Fund Advisors Lp, Neuberger Berman Group Llc, Blackrock, Inc., and several other long-term asset managers with concentrated positions in WHITE MTNS INS GROUP LTD (WTM).
This page ranks the largest institutional WTM shareholders using publicly disclosed SEC Form 13F data, including reported values, estimated current holding values, portfolio allocation percentages, ownership concentration metrics, and historical holding changes across major hedge funds and investment firms.
Institutional Holders
360
Total Reported Value
$4.60B
Largest Holder
Dimensional Fund Advisors Lp
Largest Position
$329.58M
Insider Transactions (90d)
1
Latest Filing Quarter
Q2 2026
New Institutional Positions
41
Funds Exiting Positions
0
| Name | Investor/Manager | Portfolio % | Quantity | Reported Balance | Current Estimated Value | Gain/loss Since Filing | Estimated Portfolio Performance |
|---|---|---|---|---|---|---|---|
| Dimensional Fund Advisors Lp | 0.06% | 158,954 | $329,577,765 | $360,823,990 | +$31,246,225 | +9.48% | |
| Neuberger Berman Group Llc | 0.20% | 129,654 | $269,424,901 | $294,313,283 | +$24,888,382 | +9.24% | |
| Blackrock, Inc. | 0.00% | 117,849 | $244,347,011 | $267,516,052 | +$23,169,041 | +9.48% | |
| River Road Asset Management, Llc | 2.67% | 115,880 | $240,264,433 | $263,046,441 | +$22,782,008 | +9.48% | |
| Vanguard Portfolio Management Llc | 0.01% | 111,969 | $232,155,405 | $254,168,510 | +$22,013,105 | +9.48% | |
| Vanguard Capital Management Llc | 0.00% | 107,479 | $222,845,884 | $243,976,255 | +$21,130,371 | +9.48% | |
| Fuller & Thaler Asset Management, Inc. | 0.58% | 101,892 | $211,260,919 | $231,293,821 | +$20,032,902 | +9.48% | |
| Cooke & Bieler Lp | 2.75% | 87,203 | $174,971,947 | $197,949,938 | +$22,977,991 | +13.13% | |
| Wallace Capital Management Inc. | 18.20% | 80,067 | $166,009,833 | $181,751,289 | +$15,741,456 | +9.48% | |
| Fiduciary Management Inc | 1.96% | 66,550 | $137,984,104 | $151,067,835 | +$13,083,731 | +9.48% | |
| Gendell Jeffrey L | 1.11% | 59,243 | $122,833,844 | $134,481,018 | +$11,647,174 | +9.48% | |
| Boston Partners | 0.10% | 55,569 | $115,277,291 | $126,141,074 | +$10,863,783 | +9.42% | |
| London Co Of Virginia | 0.64% | 54,025 | $112,075,761 | $122,636,210 | +$10,560,449 | +9.42% | |
| State Street Corp | 0.00% | 50,257 | $104,202,361 | $114,082,887 | +$9,880,526 | +9.48% | |
| Geode Capital Management, Llc | 0.01% | 49,412 | $102,474,687 | $112,164,746 | +$9,690,059 | +9.46% | |
| Morgan Stanley | 0.01% | 46,866 | $97,175,344 | $106,385,351 | +$9,210,007 | +9.48% | |
| Reinhart Partners, Llc. | 2.15% | 43,959 | $88,203,294 | $99,786,490 | +$11,583,196 | +13.13% | |
| T. Rowe Price Investment Management, Inc. | 0.05% | 34,237 | $70,987,000 | $77,717,648 | +$6,730,648 | +9.48% | |
| Lord, Abbett & Co. Llc | 0.19% | 32,829 | $68,067,000 | $74,521,502 | +$6,454,502 | +9.48% | |
| American Century Companies Inc | 0.03% | 31,108 | $64,499,016 | $70,614,849 | +$6,115,833 | +9.48% | |
| Norges Bank | 0.01% | 27,956 | $57,963,691 | $63,459,840 | +$5,496,149 | +9.48% | |
| Cannell & Spears Llc | 1.02% | 27,577 | $57,177,034 | $62,599,514 | +$5,422,480 | +9.48% | |
| Bank Of America Corp | 0.00% | 25,028 | $51,892,804 | $56,813,310 | +$4,920,506 | +9.48% | |
| Charles Schwab Investment Management Inc | 0.01% | 23,505 | $48,735,032 | $53,356,115 | +$4,621,083 | +9.48% | |
| Mraz, Amerine & Associates, Inc. | 6.94% | 22,147 | $44,438,117 | $50,273,469 | +$5,835,352 | +13.13% | |
| Allspring Global Investments Holdings, Llc | 0.06% | 18,116 | $37,392,149 | $41,123,139 | +$3,730,990 | +9.98% | |
| Gotham Asset Management, Llc | 0.09% | 17,940 | $37,196,617 | $40,723,621 | +$3,527,004 | +9.48% | |
| Brown Advisory Inc | 0.06% | 17,722 | $36,745,806 | $40,228,763 | +$3,482,957 | +9.48% | |
| Jane Street Group, Llc | 0.02% | 17,226 | $35,716,216 | $39,102,848 | +$3,386,632 | +9.48% | |
| Longleaf Partners | Mason Hawkins | 1.85% | 17,104 | $35,463,263 | $38,825,909 | +$3,362,646 | +9.48% |
| Ubs Group Ag | 0.01% | 16,198 | $33,584,772 | $36,769,298 | +$3,184,526 | +9.48% | |
| Vanguard Fiduciary Trust Co | 0.01% | 15,319 | $31,762,261 | $34,773,977 | +$3,011,716 | +9.48% | |
| Boussard & Gavaudan Investment Management Llp | 2.97% | 13,975 | $30,968,600 | $31,723,110 | +$754,510 | +2.44% | |
| Raymond James Financial Inc | 0.01% | 14,833 | $30,754,659 | $33,670,762 | +$2,916,103 | +9.48% | |
| Northern Trust Corp | 0.00% | 14,571 | $30,211,365 | $33,076,024 | +$2,864,659 | +9.48% | |
| Wellington Management Group Llp | 0.01% | 14,532 | $30,130,503 | $32,987,495 | +$2,856,992 | +9.48% | |
| Envestnet Asset Management Inc | 0.01% | 13,838 | $28,691,176 | $31,412,122 | +$2,720,946 | +9.48% | |
| Quantinno Capital Management Lp | 0.03% | 12,624 | $26,174,512 | $28,656,354 | +$2,481,842 | +9.48% | |
| Elkhorn Partners Limited Partnership | 21.89% | 12,320 | $25,544,165 | $27,966,277 | +$2,422,112 | +9.48% | |
| Horizon Kinetics Asset Management Llc | 0.29% | 12,206 | $25,307,802 | $27,707,498 | +$2,399,696 | +9.48% | |
| Goldman Sachs Group Inc | 0.00% | 12,151 | $25,193,682 | $27,582,648 | +$2,388,966 | +9.48% | |
| Victory Capital Management Inc | 0.01% | 10,684 | $22,152,098 | $24,252,573 | +$2,100,475 | +9.48% | |
| First Trust Advisors Lp | 0.01% | 10,604 | $21,986,231 | $24,070,974 | +$2,084,743 | +9.48% | |
| Qube Research & Technologies Ltd | 0.02% | 9,673 | $20,055,901 | $21,957,613 | +$1,901,712 | +9.48% | |
| Speece Thorson Capital Group Inc | 4.08% | 9,215 | $19,106,000 | $20,917,958 | +$1,811,958 | +9.48% | |
| Wells Fargo & Company/Mn | 0.00% | 8,710 | $18,058,335 | $19,771,613 | +$1,713,278 | +9.49% | |
| Bank Of New York Mellon Corp | 0.00% | 8,412 | $17,440,426 | $19,095,156 | +$1,654,730 | +9.49% | |
| Ubs Am, A Distinct Business Unit Of Ubs Asset Management Americas Llc | 0.00% | 7,826 | $17,193,410 | $17,764,942 | +$571,532 | +3.32% | |
| Sei Investments Co | 0.01% | 8,108 | $16,810,842 | $18,405,079 | +$1,594,237 | +9.48% | |
| Gw&K Investment Management, Llc | 0.13% | 7,839 | $16,253,000 | $17,794,452 | +$1,541,452 | +9.48% |
Frequently asked questions about WTM
Who are the largest institutional holders of WTM?
The largest institutional holders of WTM reported in the latest SEC Form 13F filings include Dimensional Fund Advisors Lp, Neuberger Berman Group Llc, Blackrock, Inc., River Road Asset Management, Llc, and Vanguard Portfolio Management Llc. InsiderSet ranks institutional holders by their latest reported WTM position.
What is WTM institutional ownership?
This page tracks WTM positions reported by institutional investment managers through SEC Form 13F. WHITE MTNS INS GROUP LTD (WTM) institutional ownership on InsiderSet reflects disclosed 13F holdings among the managers we analyze, not every shareholder of the stock.
How many institutions own WTM?
InsiderSet currently tracks 360 institutional managers reporting WTM holdings in the latest available 13F data. This count reflects institutions included in the SEC Form 13F filings analyzed by InsiderSet and should not be interpreted as the total number of WTM shareholders.
How much WTM stock do institutions own?
Institutional investment managers disclosed approximately $4.60B in WTM holdings for Q2 2026. This figure is reported 13F value as of the filing period, not necessarily today's market value.
When was WTM institutional ownership last updated?
The latest WTM institutional ownership data on InsiderSet is based on SEC Form 13F filings for the quarter ended June 30, 2026. Form 13F filings are generally reported after the quarter ends, so the holdings shown represent the latest publicly disclosed positions rather than real-time institutional holdings.
Are institutional WTM holdings real-time?
No. Form 13F data is not real-time. It represents positions reported by institutional investment managers as of the end of the reporting quarter. An institution may have changed its WTM position after the reporting date.
Are institutions buying or selling WTM?
Institutional buying and selling can be analyzed by comparing WTM positions across consecutive 13F reporting periods. InsiderSet's WTM Ownership Changes page shows institutions that increased, reduced, initiated, or exited positions based on reported 13F holdings. View WTM ownership changes.
How has WTM institutional ownership changed over time?
InsiderSet tracks WTM institutional holdings across multiple 13F reporting periods, allowing investors to compare institutional holder counts, reported value, and reported shares over time.