Arkolith/Funds/White Mountains Insurance Group Ltd

White Mountains Insurance Group Ltd

CIK 776867Insurance
Holdings as of Jun 30, 2026·disclosed Aug 12, 2026·~43-day 13F lag·13F-HR
Active Filer

White Mountains Insurance Group Ltd holds a concentrated book of 2 stocks worth $393.6M as of Q2 2026 (disclosed Aug 12, 2026, a ~43-day 13F lag). Their largest long position is Mediaalpha Inc-Class A at 57% of the equity book.

Opened
0
bought for the first time
no new positions
Added to
0
already held, bought more
no adds
Trimmed
0
sold some, still holds it
no trims
Sold out
0
exited the position entirely
nothing exited

Concentration

Top-heavy: concentrated book

Top 5 holdings
100%
Top 10 holdings
100%
Top 20 holdings
100%

Share of the disclosed book in its largest positions. A higher top-5 share means a more concentrated, higher-conviction portfolio.

Direct sector allocation

57% mapped to company sectors

Industrials
57%
ETF / fund or unclassified
43%

Direct operating-company sectors from our SIC-based security master. ETF/fund and unclassified holdings stay visible separately; this is not ETF look-through exposure.

Funds with the most overlap

Other tracked managers holding the same core names as White Mountains Insurance Group Ltd

Manager / fundShared namesTheir $ in those
JPMORGAN CHASE & CO2 / 2$29.0B
MORGAN STANLEY2 / 2$26.3B
GOLDMAN SACHS GROUP INC2 / 2$23.8B
BANK OF AMERICA CORP /DE/2 / 2$21.0B
JANE STREET GROUP, LLC2 / 2$13.2B
NORTHERN TRUST CORP2 / 2$9.0B
UBS Group AG2 / 2$8.0B
SUSQUEHANNA INTERNATIONAL GROUP, LLP2 / 2$6.9B

Ranked by how many of White Mountains Insurance Group Ltd's top 2 disclosed names each fund also holds: a cross-fund conviction signal from the latest 13F of every tracked manager.

Holdings: largest first

Bars show each stock's share of the portfolio. Click a row for its position history.

2 positions
#SecurityValueShares% PortLast moveHistory
1Mediaalpha Inc
CL A
$224.5M17.86M
57.0%
—Held
2SPDR S&P 500 ETF TR
TR UNIT
$169.1M226.5K
43.0%
—Held
Showing all 2 positions
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Filing history

As-of date vs the date the SEC received each filing

QuarterAs ofFiledPositionsValueForm
Q2 2026Jun 30, 2026Aug 12, 20262$393.6M13F-HR
Q1 2026Mar 31, 2026May 12, 20262$313.4M13F-HR
Q4 2025Dec 31, 2025Feb 12, 20262$261.9M13F-HR
Q3 2025Sep 30, 2025Nov 13, 20251$203.2M13F-HR
Q2 2025Jun 30, 2025Aug 11, 20251$195.5M13F-HR
Q1 2025Mar 31, 2025May 12, 20252$285.9M13F-HR
Q4 2024Dec 31, 2024Feb 12, 20252$426.2M13F-HR
Q3 2024Sep 30, 2024Nov 12, 20242$543.2M13F-HR

Data source

Holdings from SEC EDGAR 13F-HR filings, updated quarterly, filed up to 45 days after quarter-end. Public domain. The book and weighting are long equity only; disclosed put/call options are listed separately and excluded from those totals. Price-derived performance is withheld until the price-source policy and freshness gate are green.