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

SecurityWTM / White Mountains Insurance Group, Ltd.
InstitutionAmalgamated Bank
Latest Disclosed Ownership132 shares
Latest Disclosed Value $ 290
Amalgamated Bank reports 3.94% increase in ownership of WTM / White Mountains Insurance Group, Ltd.

On May 8, 2026 - Amalgamated Bank filed a 13F-HR form disclosing ownership of 132 shares of White Mountains Insurance Group, Ltd. (US:WTM) valued at $289,999 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 5, 2026 disclosing 127 shares of White Mountains Insurance Group, Ltd.. The current value of the position is $272,598 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)
2026-05-08 2026-03-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 132 5 3.94 0 0.0022
2026-02-05 2025-12-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 127 2 1.60 0 0.0019
2025-10-29 2025-09-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 125 -5 -3.85 0 0.0015
2025-08-04 2025-06-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 130 -4 -2.99 0 0.0018
2025-04-25 2025-03-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 134 2 1.52 0 0.0022
2025-02-04 2024-12-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 132 -2 -1.49 0 0.0021
2024-10-30 2024-09-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 134 -305 -69.48 0 0.0019
2024-08-12 2024-06-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 439 301 218.12 1 0.0068
2024-04-23 2024-03-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 138 -270 -66.18 0 0.0021
2024-02-06 2023-12-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 408 -17 -4.00 1 0.0049
2023-11-08 2023-09-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 425 48 12.73 1 0.0054
2023-08-11 2023-06-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 377 -38 -9.16 1 0.0042
2023-05-02 2023-03-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 415 -77 -15.65 1 0.0049
2023-02-10 2022-12-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 492 -27 -5.20 1 -100.00 0.0062
2022-11-09 2022-09-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 519 -3 -0.57 676 4.00 0.0065
2022-08-15 2022-06-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 522 -83 -13.72 650 -5.39 0.0061
2022-08-25 2022-03-31 13F/A-1 WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 605 -23 -3.66 687 7.85 0.0053
2022-06-30 2022-03-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 605 -23 687 0.0055
2022-02-15 2021-12-31 13F/A-1 WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 628 -5 -0.79 637 -5.91 0.0047
2022-02-15 2021-12-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 628 -5 637 0.0047
2021-10-29 2021-09-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 633 -27 -4.09 677 -10.69 0.0057
2021-08-16 2021-06-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 660 301 83.84 758 89.50 0.0061
2021-05-13 2021-03-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 359 -17 -4.52 400 6.38 0.0150
2021-02-12 2020-12-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 376 0 0.00 376 28.33 0.0142
2020-10-30 2020-09-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 376 -1 -0.27 293 -12.54 0.0127
2020-08-10 2020-06-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 377 -291 -43.56 335 -44.90 0.0155
2020-05-13 2020-03-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 668 -17 -2.48 608 -20.42 0.0149
2020-02-13 2019-12-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 685 72 11.75 764 15.41 0.0141
2019-11-13 2019-09-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 613 -6 -0.97 662 4.75 0.0139
2019-08-14 2019-06-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 619 21 3.51 632 14.29 0.0148
2019-05-15 2019-03-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 598 14 2.40 553 10.38 0.0134
2019-02-15 2018-12-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 584 4 0.69 501 -7.73 0.0142
2018-11-14 2018-09-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 580 -2 -0.34 543 2.84 0.0134
2018-07-18 2018-06-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 582 -97 -14.29 528 -5.38 0.0129
2018-05-22 2018-03-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 679 -6 -0.88 558 -4.29 0.0148
2018-02-13 2017-12-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 685 -101 -12.85 583 -13.50 0.0158
2017-11-09 2017-09-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 786 -3 -0.38 674 -1.61 0.0210
2017-08-10 2017-06-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 789 180 29.56 685 27.80 0.0225
2017-05-12 2017-03-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 609 20 3.40 536 8.94 0.0267
2017-02-14 2016-12-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 589 20 3.51 492 4.24 0.0222
2016-11-15 2016-09-30 13F/A-1 WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 569 2 0.35 472 0.85 0.0274
2016-08-16 2016-06-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 567 -99 -14.86 468 -12.52 0.0271
2016-05-11 2016-03-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 666 60 9.90 535 21.59 0.0521
2016-02-10 2015-12-31 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 606 -72 -10.62 440 -13.21 0.0543
2015-11-04 2015-09-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 678 6 0.89 507 15.23 0.0532
2015-07-10 2015-06-30 13F WHITE MOUNTAINS INSURANCE GROUP COM G9618E107 672 672 440 0.0432
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.