White Mountains Insurance Group, Ltd.
US ˙ NYSE ˙ BMG9618E1075

SecurityWTM / White Mountains Insurance Group, Ltd.
InstitutionStrs Ohio
Latest Disclosed Ownership59 shares
Latest Disclosed Value $ 129,621
Strs Ohio ownership in WTM / White Mountains Insurance Group, Ltd.

On April 24, 2026 - Strs Ohio filed a 13F-HR form disclosing ownership of 59 shares of White Mountains Insurance Group, Ltd. (US:WTM) valued at $129,621 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 2, 2026 disclosing 59 shares of White Mountains Insurance Group, Ltd.. This represents a change in shares of 0.00% during the quarter. The current value of the position is $118,917 USD.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-04-24 2026-03-31 13F WHITE MOUNTAINS INSURANCE GP COM_STK G9618E107 59 0 0.00 130 5.74 0.0005
2026-02-02 2025-12-31 13F WHITE MOUNTAINS INSURANCE GP COM_STK G9618E107 59 -1 -1.67 123 22.00 0.0005
2025-10-30 2025-09-30 13F WHITE MOUNTAINS INSURANCE GP COM_STK G9618E107 60 -1,515 -96.19 100 -96.46 0.0004
2025-08-04 2025-06-30 13F WHITE MOUNTAINS INSURANCE GP COM_STK G9618E107 1,575 430 37.55 2,828 28.25 0.0106
2025-05-28 2025-03-31 13F WHITE MOUNTAINS INSURANCE GP COM_STK G9618E107 1,145 -356 -23.72 2,205 -24.46 0.0092
2025-05-28 2024-12-31 13F WHITE MOUNTAINS INSURANCE GP COM_STK G9618E107 1,501 2 0.13 2,920 14.83 0.0116
2024-11-01 2024-09-30 13F WHITE MOUNTAINS INSURANCE GP COM_STK G9618E107 1,499 152 11.28 2,543 3.84 0.0098
2024-08-05 2024-06-30 13F WHITE MOUNTAINS INSURANCE GP COM_STK G9618E107 1,347 -120 -8.18 2,448 122,300.00 0.0097
2024-05-13 2024-03-31 13F WHITE MTNS INS GROUP COM G9618E107 1,467 -438 -22.99 3 0.00 0.0105
2024-01-30 2023-12-31 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 1,905 237 14.21 3 0.00 0.0119
2023-10-26 2023-09-30 13F/A-1 WHITE MOUNTAINS INSURANCE GP COM G9618E107 1,668 -475 -22.17 2 0.00 0.0111
2023-10-26 2023-09-30 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 1,668 -475 2 0.0111
2023-07-31 2023-06-30 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 2,143 -258 -10.75 3 -33.33 0.0126
2023-08-02 2023-03-31 13F/A-2 WHITE MOUNTAINS INSURANCE GP COM G9618E107 2,401 -54 -2.20 3 0.00 0.0143
2023-08-02 2023-03-31 13F/A-1 WHITE MOUNTAINS INSURANCE GP COM G9618E107 2,401 -54 3 0.0143
2023-04-27 2023-03-31 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 2,401 -54 3 0.0171
2023-01-26 2022-12-31 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 2,455 352 16.74 3 -99.89 0.0157
2022-10-27 2022-09-30 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 2,103 116 5.84 2,740 10.66 0.0131
2022-07-25 2022-06-30 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 1,987 63 3.27 2,476 13.27 0.0112
2022-04-21 2022-03-31 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 1,924 -104 -5.13 2,186 6.32 0.0080
2022-01-24 2021-12-31 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 2,028 47 2.37 2,056 -2.93 0.0071
2021-10-22 2021-09-30 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 1,981 -237 -10.69 2,118 -16.81 0.0080
2021-07-26 2021-06-30 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 2,218 414 22.95 2,546 26.60 0.0092
2021-04-23 2021-03-31 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 1,804 1,804 2,011 0.0076
2021-01-25 2020-12-31 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 0 -2,094 -100.00 0 -100.00
2020-12-14 2020-09-30 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 2,094 -16 -0.76 1,631 -12.92 0.0068
2020-07-23 2020-06-30 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 2,110 683 47.86 1,873 44.30 0.0082
2020-04-23 2020-03-31 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 1,427 -137 -8.76 1,298 -25.57 0.0068
2020-01-24 2019-12-31 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 1,564 779 99.24 1,744 105.90 0.0073
2019-10-21 2019-09-30 13F/A-1 WHITE MOUNTAINS INSURANCE GP COM G9618E107 785 80 11.35 847 17.64 0.0037
2019-10-21 2019-09-30 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 785 -779 847 3,748.8690
2019-07-25 2019-06-30 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 705 -91 -11.43 720 -2.17 0.0032
2019-04-19 2019-03-31 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 796 -102 -11.36 736 -4.42 0.0033
2019-01-23 2018-12-31 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 898 154 20.70 770 10.63 0.0039
2018-10-19 2018-09-30 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 744 46 6.59 696 10.13 0.0031
2018-08-06 2018-06-30 13F WHITE MOUNTAINS INSURANCE GP COM G9618E107 698 698 632 0.0027
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.