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$WTM
$2,227.34 +$2.10 (0.09%) Close

Ownership

13F as of Q2 2026 · 2.4M shares outstanding

Who owns WTM?

By type of holder
Institutions 92.2% Insiders 2.6% Everyone else 5.2%
Concentration Top 10 holders own 44.6%
Dimensional Fund Advisors LP 6.7% · Neuberger Berman Group LLC 5.0%
Institutional ownership
92.2%
-0.3 pts vs last qtr
Institutional holders
354
-11 vs last qtr
Net shares bought
−6.7K
by institutions in Q2 2026
New / sold out
39 / 50
positions opened vs closed

How is ownership changing?

Institutions, last 8 quarters

Biggest buyers in Q2 2026
  • Norges Bank NEW +28.0K
  • American Century Companies Inc +22.8K

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Biggest sellers in Q2 2026
  • Cooke & Bieler LP −19.7K
  • Fiduciary Management Inc /wi/ −18.5K

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Who is planning to sell?

No insider has filed a notice of proposed sale (Form 144) for White Mountains Insurance Group, Ltd. in the last 12 months.

Is your stake being diluted?

Diluted share count, FY2016–FY2025
−48.8%
−7.18% a year
Each share's claim on the business
+95.5%
grew without buying or selling a share
Spent on buybacks vs paid in stock
$3.16B vs $78.8M
over 10 fiscal years
Diluted shares, split-adjusted
2.5M3.7M5.0M2016: 5.0M shares'162017: 4.2M shares'172018: 3.3M shares'182019: 3.1M shares'192020: 3.1M shares'202021: 3.0M shares'212022: 2.8M shares'222023: 2.5M shares'232024: 2.5M shares'242025: 2.5M shares'25
Buybacks Stock-based comp
$0$440.7M$881.3M2016 buybacks: $881.3M2016 stock comp: $0'162017 buybacks: $714.6M2017 stock comp: $0'172018 buybacks: $511.9M2018 stock comp: $0'182019 buybacks: $02019 stock comp: $0'192020 buybacks: $85.2M2020 stock comp: $0'202021 buybacks: $107.5M2021 stock comp: $14.7M'212022 buybacks: $615.8M2022 stock comp: $14.0M'222023 buybacks: $32.7M2023 stock comp: $15.3M'232024 buybacks: $7.9M2024 stock comp: $16.3M'242025 buybacks: $202.6M2025 stock comp: $18.5M'25

How patient are the owners?

Institutional shares by how long they've been held
5+ years75% 3–5 years6% 1–3 years11% Under 1 year7%
Quarterly turnover
8.9%
of institutional shares changed hands
Top 10 managers, median time held
5 years

Super Investors

Investment managers reporting WTM on Form 13F
DF
Dimensional Fund Advisors LP
Shares
159.0K
% of company
6.66%
Change vs last qtr
+2.3K (+1.5%)
Held since
≤2021
NB
Neuberger Berman Group LLC
Shares
119.1K
% of company
4.99%
Change vs last qtr
−5.6K (−4.5%)
Held since
≤2021

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Institutional Funds

Mutual funds and ETFs reporting WTM on Form N-PORT; together they hold 16.6% of the company
VT
Vanguard Total Stock Market Index Fund
Vanguard Index Funds
Position value
$155M
% of company
3.13%
% of the fund
0.01%
As of
June 30, 2026
VS
Vanguard Small-Cap Index Fund
Vanguard Index Funds
Position value
$112M
% of company
2.26%
% of the fund
0.06%
As of
June 30, 2026

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Insiders and 5%+ holders

From Forms 3/4/5 and Schedules 13D/G
SR
Seelig Robert Lawrence
Insider
Shares
19.0K
% of company
0.80%
Change vs last qtr
—
Held since
—
RG
Rountree George Manning
Insider
Shares
13.9K
% of company
0.58%
Change vs last qtr
—
Held since
—

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