Arthur J. Gallagher & Co.
MX ˙ BMV ˙ US3635761097
SecurityMX:AJG / Arthur J. Gallagher & Co.
InstitutionBoston Partners
Latest Disclosed Ownership808,257 shares
Latest Disclosed Value $ 175,106,160
Boston Partners reports 2.64% decrease in ownership of AJG / Arthur J. Gallagher & Co.

On May 11, 2026 - Boston Partners filed a 13F-HR form disclosing ownership of 808,257 shares of Arthur J. Gallagher & Co. (MX:AJG) valued at $175,106,160 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 13, 2026 disclosing 830,159 shares of Arthur J. Gallagher & Co.. This represents a change in shares of -2.64% during the quarter.

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)
2026-05-11 2026-03-31 13F GALLAGHER ARTHUR J COM 363576109 808,257 -21,902 -2.64 175,106 -18.47 0.0784
2026-02-13 2025-12-31 13F GALLAGHER ARTHUR J COM 363576109 830,159 -202,094 -19.58 214,765 -32.80 0.2224
2025-11-13 2025-09-30 13F GALLAGHER ARTHUR J COM 363576109 1,032,253 294,954 40.00 319,587 36.16 0.3281
2025-08-12 2025-06-30 13F/A-1 GALLAGHER ARTHUR J COM 363576109 737,299 4,346 0.59 234,719 -7.04 0.2607
2025-08-07 2025-06-30 13F GALLAGHER ARTHUR J COM 363576109 735,759 2,806 234,226 0.1075
2025-05-13 2025-03-31 13F GALLAGHER ARTHUR J COM 363576109 732,953 55,840 8.25 252,499 31.14 0.3054
2025-02-11 2024-12-31 13F GALLAGHER ARTHUR J COM 363576109 677,113 -208,978 -23.58 192,541 -22.89 0.2342
2024-11-12 2024-09-30 13F GALLAGHER ARTHUR J COM 363576109 886,091 -7,284 -0.82 249,692 7.55 0.2947
2024-08-14 2024-06-30 13F GALLAGHER ARTHUR J COM 363576109 893,375 -717,924 -44.56 232,171 -42.28 0.2884
2024-05-28 2024-03-31 13F/A-1 GALLAGHER ARTHUR J COM 363576109 1,611,299 38,886 2.47 402,206 13.57 0.4791
2024-05-13 2024-03-31 13F GALLAGHER ARTHUR J COM 363576109 1,611,299 38,886 402,206 0.1990
2024-02-07 2023-12-31 13F GALLAGHER ARTHUR J COM 363576109 1,572,413 -464,844 -22.82 354,142 -23.82 0.4690
2023-11-08 2023-09-30 13F GALLAGHER ARTHUR J COM 363576109 2,037,257 -140,558 -6.45 464,890 -2.80 0.6436
2023-08-10 2023-06-30 13F GALLAGHER ARTHUR J COM 363576109 2,177,815 -3,618 -0.17 478,271 14.22 0.6438
2023-05-09 2023-03-31 13F GALLAGHER ARTHUR J COM 363576109 2,181,433 2,181,433 418,715 0.5756
2022-11-09 2022-09-30 13F GALLAGHER ARTHUR J COM 363576109 0 -2,972 -100.00 0 -100.00
2022-08-10 2022-06-30 13F GALLAGHER ARTHUR J COM 363576109 2,972 -494 -14.25 485 -19.83 0.0007
2022-05-10 2022-03-31 13F GALLAGHER ARTHUR J COM 363576109 3,466 101 3.00 605 5.95 0.0007
2022-02-04 2021-12-31 13F GALLAGHER ARTHUR J COM 363576109 3,365 -1,479 -30.53 571 -20.69 0.0007
2021-11-05 2021-09-30 13F GALLAGHER ARTHUR J COM 363576109 4,844 -698 -12.59 720 -7.22 0.0009
2021-08-12 2021-06-30 13F GALLAGHER ARTHUR J COM 363576109 5,542 -778 -12.31 776 -1.65 0.0010
2021-05-10 2021-03-31 13F GALLAGHER ARTHUR J COM 363576109 6,320 -530 -7.74 789 -6.85 0.0011
2021-02-10 2020-12-31 13F/A-1 GALLAGHER ARTHUR J COM 363576109 6,850 -1,387 -16.84 847 -2.64 0.0013
2021-02-04 2020-12-31 13F GALLAGHER ARTHUR J COM 363576109 6,850 -1,387 847 508.1497
2020-11-13 2020-09-30 13F/A-1 GALLAGHER ARTHUR J COM 363576109 8,237 -79 -0.95 870 7.27 0.0016
2020-11-09 2020-09-30 13F GALLAGHER ARTHUR J COM 363576109 8,316 0 811 595.3706
2020-08-12 2020-06-30 13F GALLAGHER ARTHUR J COM 363576109 8,316 -2,407 -22.45 811 -7.21 0.0015
2020-05-13 2020-03-31 13F GALLAGHER ARTHUR J COM 363576109 10,723 -7,978 -42.66 874 -50.93 0.0017
2020-02-06 2019-12-31 13F/A-1 GALLAGHER ARTHUR J COM 363576109 18,701 -5,607 -23.07 1,781 -18.19 0.0024
2020-02-05 2019-12-31 13F GALLAGHER ARTHUR J COM 363576109 18,701 -5,607 1,781 1,001.3302
2019-11-20 2019-09-30 13F/A-1 GALLAGHER ARTHUR J COM 363576109 24,308 -4,746 -16.34 2,177 -14.46 0.0029
2019-11-08 2019-09-30 13F GALLAGHER ARTHUR J COM 363576109 29,054 0 2,545 0.0034
2019-08-26 2019-06-30 13F/A-1 GALLAGHER ARTHUR J COM 363576109 29,054 -2,699 -8.50 2,545 2.62 0.0033
2019-08-09 2019-06-30 13F GALLAGHER ARTHUR J COM 363576109 29,054 -2,699 2,545
2019-05-13 2019-03-31 13F/A-1 GALLAGHER ARTHUR J COM 363576109 31,753 -5,527 -14.83 2,480 -9.75 0.0033
2019-05-03 2019-03-31 13F GALLAGHER ARTHUR J COM 363576109 31,753 -5,527 2,480
2019-02-07 2018-12-31 13F GALLAGHER ARTHUR J COM 363576109 37,280 -17,542 -32.00 2,748 -32.66 0.0039
2018-11-14 2018-09-30 13F GALLAGHER ARTHUR J COM 363576109 54,822 -1,531 -2.72 4,081 10.93 0.0047
2018-08-03 2018-06-30 13F GALLAGHER ARTHUR J COM 363576109 56,353 56,353 3,679 0.0044
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.