WHITE MOUNTAINS INSURANCE GROUP LTD
Long book
$313.4M
Q1 2026
Positions
2
Top-10 weight
100%
concentration
Last quarter
+30.5%
SPY +14.8%
Turnover
0%
of book per quarter
Strategy in plain words
auto-generated from filingsWHITE MOUNTAINS INSURANCE GROUP LTD is an institutional manager, specialised in services_media (100% of the long book), running a $313.4M US long book across 2 positions.
The portfolio is extremely concentrated — the top 10 positions are almost the whole book. The book barely moves quarter to quarter — a patient, low-turnover holder. Current anchor positions: MEDIAALPHA INC-CLASS A, SS SPDR S&P 500 ETF TRUST-US.
Over the last 9 quarters its long book ran on average 4.2pp per quarter behind the S&P 500, beating the index in 4 of 9 quarters. Signal value of individual moves is limited — treat changes as weak evidence.
Implied long-book return vs S&P 500
methodology: positions priced quarterly, no shorts/options Fund long book S&P 500
Q1 2024
-25.6%
Q2 2024
+22.6%
Q3 2024
-21.4%
Q4 2024
-10.8%
Q1 2025
+15.2%
Q2 2025
+3.9%
Q3 2025
+13.8%
Q4 2025
-25.4%
Q1 2026
+30.5%
Sector allocation
Services media 100%
Long book by quarter
What does WHITE MOUNTAINS own?
Q1 2026 13F| Company | Sector | Shares | Value | % of book | Change |
|---|---|---|---|---|---|
| MAX MEDIAALPHA INC-CLASS A | Services media | 17.9M | $166.1M | 53.0% | Held |
13F filing history
| Period | Form | Filed | Entries | Reported value | Flags | Source |
|---|---|---|---|---|---|---|
| Q1 2026 | 13F-HR | May 12, 2026 | 2 | $313.4M | canonical | SEC ↗ |
| Q4 2025 | 13F-HR | Feb 12, 2026 | 2 | $261.9M | canonical | SEC ↗ |
| Q3 2025 | 13F-HR | Nov 13, 2025 | 1 | $203.2M | canonical | SEC ↗ |
| Q2 2025 | 13F-HR | Aug 11, 2025 | 1 | $195.5M | canonical | SEC ↗ |
| Q1 2025 | 13F-HR | May 12, 2025 | 2 | $285.9M | canonical | SEC ↗ |
| Q4 2024 | 13F-HR | Feb 12, 2025 | 2 | $426.2M | canonical | SEC ↗ |
| Q3 2024 | 13F-HR | Nov 12, 2024 | 2 | $543.2M | canonical | SEC ↗ |
| Q2 2024 | 13F-HR | Aug 8, 2024 | 2 | $443.7M | canonical | SEC ↗ |
| Q1 2024 | 13F-HR | May 9, 2024 | 2 | $617.2M | canonical | SEC ↗ |
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