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

SecurityWTM / White Mountains Insurance Group, Ltd.
InstitutionSei Investments Co
Latest Disclosed Ownership7,916 shares
Latest Disclosed Value $ 16,450,024
Sei Investments Co reports 46.97% increase in ownership of WTM / White Mountains Insurance Group, Ltd.

On February 13, 2026 - Sei Investments Co filed a 13F-HR form disclosing ownership of 7,916 shares of White Mountains Insurance Group, Ltd. (US:WTM) valued at $16,449,685 USD as of December 31, 2025. The entity filed a previous 13F-HR on November 13, 2025 disclosing 5,386 shares of White Mountains Insurance Group, Ltd.. This represents a change in shares of 46.97% during the quarter. The current value of the position is $16,101,302 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)
2026-02-13 2025-12-31 13F WHITE MTNS INS GROUP COM G9618E107 7,916 2,530 46.97 16,450 82.74 0.0162
2025-11-13 2025-09-30 13F WHITE MTNS INS GROUP COM G9618E107 5,386 481 9.81 9,002 2.20 0.0097
2025-08-14 2025-06-30 13F WHITE MTNS INS GROUP COM G9618E107 4,905 805 19.63 8,809 11.55 0.0102
2025-05-14 2025-03-31 13F/A-1 WHITE MTNS INS GROUP COM G9618E107 4,100 883 27.45 7,897 26.17 0.0102
2025-05-13 2025-03-31 13F WHITE MTNS INS GROUP COM G9618E107 3,083 -134 5,974 0.0065
2025-02-11 2024-12-31 13F WHITE MTNS INS GROUP COM G9618E107 3,217 731 29.40 6,259 48.40 0.0080
2024-11-12 2024-09-30 13F WHITE MTNS INS GROUP COM G9618E107 2,486 97 4.06 4,217 -2.86 0.0055
2024-08-13 2024-06-30 13F WHITE MTNS INS GROUP COM G9618E107 2,389 -29 -1.20 4,342 0.09 0.0062
2024-05-07 2024-03-31 13F WHITE MTNS INS GROUP COM G9618E107 2,418 395 19.53 4,338 42.43 0.0064
2024-02-14 2023-12-31 13F WHITE MTNS INS GROUP COM G9618E107 2,023 284 16.33 3,046 17.07 0.0049
2023-11-14 2023-09-30 13F WHITE MTNS INS GROUP COM G9618E107 1,739 -20 -1.14 2,602 6.47 0.0047
2023-08-11 2023-06-30 13F WHITE MTNS INS GROUP COM G9618E107 1,759 -16 -0.90 2,444 -0.08 0.0043
2023-05-12 2023-03-31 13F WHITE MTNS INS GROUP COM G9618E107 1,775 155 9.57 2,445 6.77 0.0045
2023-02-10 2022-12-31 13F WHITE MTNS INS GROUP COM G9618E107 1,620 192 13.45 2,290 23.05 0.0051
2022-11-14 2022-09-30 13F WHITE MTNS INS GROUP COM G9618E107 1,428 -171 -10.69 1,861 -2.51 0.0042
2022-08-15 2022-06-30 13F WHITE MTNS INS GROUP COM G9618E107 1,599 -57 -3.44 1,909 4.26 0.0041
2022-05-13 2022-03-31 13F WHITE MTNS INS GROUP COM G9618E107 1,656 -372 -18.34 1,831 -10.38 0.0037
2022-02-14 2021-12-31 13F WHITE MTNS INS GROUP COM G9618E107 2,028 378 22.91 2,043 19.13 0.0038
2021-11-12 2021-09-30 13F WHITE MTNS INS GROUP COM G9618E107 1,650 -23 -1.37 1,715 -6.74 0.0036
2021-08-06 2021-06-30 13F WHITE MTNS INS GROUP COM G9618E107 1,673 -470 -21.93 1,839 -17.90 0.0041
2021-05-12 2021-03-31 13F WHITE MTNS INS GROUP COM G9618E107 2,143 -66 -2.99 2,240 1.36 0.0056
2021-02-08 2020-12-31 13F WHITE MTNS INS GROUP COM G9618E107 2,209 -214 -8.83 2,210 9.84 0.0057
2020-12-04 2020-09-30 13F/A-1 WHITE MTNS INS GROUP COM G9618E107 2,423 -1,709 -41.36 2,012 -46.67 0.0058
2020-11-06 2020-09-30 13F WHITE MTNS INS GROUP COM G9618E107 3,305 -827 2,699 6,498.5919
2020-08-17 2020-06-30 13F/A-1 WHITE MTNS INS GROUP COM G9618E107 4,132 116 2.89 3,773 1.97 0.0117
2020-08-11 2020-06-30 13F WHITE MTNS INS GROUP COM G9618E107 4,736 720 4,739 12,854.7898
2020-05-14 2020-03-31 13F WHITE MTNS INS GROUP COM G9618E107 4,016 573 16.64 3,700 -2.30 0.0136
2020-02-06 2019-12-31 13F WHITE MTNS INS GROUP COM G9618E107 3,443 1,068 44.97 3,787 50.46 0.0113
2019-11-12 2019-09-30 13F WHITE MTNS INS GROUP COM G9618E107 2,375 0 0.00 2,517 4.61 0.0064
2019-08-14 2019-06-30 13F WHITE MTNS INS GROUP COM G9618E107 2,375 127 5.65 2,406 13.12 0.0079
2019-05-15 2019-03-31 13F WHITE MTNS INS GROUP COM G9618E107 2,248 340 17.82 2,127 26.31 0.0071
2019-02-13 2018-12-31 13F WHITE MTNS INS GROUP COM G9618E107 1,908 960 101.27 1,684 82.45 0.0060
2018-11-08 2018-09-30 13F WHITE MTNS INS GROUP COM G9618E107 948 -5,353 -84.95 923 -83.85 0.0033
2018-08-03 2018-06-30 13F WHITE MTNS INS GROUP COM G9618E107 6,301 427 7.27 5,714 18.23 0.0194
2018-05-11 2018-03-31 13F WHITE MTNS INS GROUP COM G9618E107 5,874 1,154 24.45 4,833 20.31 0.0185
2018-02-08 2017-12-31 13F WHITE MTNS INS GROUP COM G9618E107 4,720 -39 -0.82 4,017 -1.52 0.0139
2017-11-06 2017-09-30 13F WHITE MTNS INS GROUP COM G9618E107 4,759 1,136 31.36 4,079 29.57 0.0145
2017-07-31 2017-06-30 13F WHITE MTNS INS GROUP COM G9618E107 3,623 2,082 135.11 3,148 132.15 0.0125
2017-05-05 2017-03-31 13F WHITE MTNS INS GROUP COM G9618E107 1,541 -104 -6.32 1,356 -1.38 0.0059
2017-02-02 2016-12-31 13F WHITE MTNS INS GROUP COM G9618E107 1,645 35 2.17 1,375 2.92 0.0067
2016-11-04 2016-09-30 13F WHITE MTNS INS GROUP COM G9618E107 1,610 522 47.98 1,336 45.85 0.0068
2016-08-11 2016-06-30 13F WHITE MTNS INS GROUP COM G9618E107 1,088 755 226.73 916 243.07 0.0055
2016-05-10 2016-03-31 13F/A-1 WHITE MTNS INS GROUP COM G9618E107 333 -118 -26.16 267 -18.60 0.0017
2016-02-03 2015-12-31 13F WHITE MTNS INS GROUP COM G9618E107 451 94 26.33 328 23.31 0.0020
2015-11-02 2015-09-30 13F/A-1 WHITE MTNS INS GROUP COM G9618E107 357 85 31.25 266 49.44 0.0024
2015-10-30 2015-09-30 13F WHITE MTNS INS GROUP COM G9618E107 357 268
2015-08-07 2015-06-30 13F/A-1 WHITE MTNS INS GROUP COM G9618E107 272 -58 -17.58 178 -18.72 0.0016
2015-08-04 2015-06-30 13F WHITE MTNS INS GROUP COM G9618E107 272 -58 178 0.0016
2015-05-14 2015-03-31 13F/A-1 WHITE MTNS INS GROUP COM G9618E107 330 130 65.00 219 65.91 0.0019
2015-05-01 2015-03-31 13F WHITE MTNS INS GROUP COM G9618E107 330 219
2015-02-10 2014-12-31 13F WHITE MTNS INS GROUP COM G9618E107 200 200 132 0.0012
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.