Merck & Co., Inc.
MX ˙ BMV ˙ US58933Y1055
SecurityMX:MRK / Merck & Co., Inc.
InstitutionGFS Advisors, LLC
Latest Disclosed Ownership79,014 shares
Latest Disclosed Value $ 9,504,594
GFS Advisors, LLC reports 0.56% decrease in ownership of MRK / Merck & Co., Inc.

On May 11, 2026 - GFS Advisors, LLC filed a 13F-HR/A form disclosing ownership of 79,014 shares of Merck & Co., Inc. (MX:MRK) valued at $9,504,594 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 11, 2026 disclosing 79,462 shares of Merck & Co., Inc.. This represents a change in shares of -0.56% 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/A-1 MERCK COM 58933Y105 79,014 -448 -0.56 9,505 13.63 1.2113
2026-02-11 2025-12-31 13F MERCK COM 58933Y105 79,462 -52,355 -39.72 8,364 -24.40 0.9934
2025-11-06 2025-09-30 13F MERCK COM 58933Y105 131,817 3 0.00 11,063 6.03 1.4116
2025-07-25 2025-06-30 13F MERCK COM 58933Y105 131,814 49,440 60.02 10,434 41.11 1.4277
2025-04-21 2025-03-31 13F MERCK COM 58933Y105 82,374 -187 -0.23 7,394 -9.97 1.4846
2025-01-23 2024-12-31 13F MERCK COM 58933Y105 82,561 1,675 2.07 8,213 -10.58 1.2489
2024-10-29 2024-09-30 13F MERCK COM 58933Y105 80,886 79,926 8,325.62 9,185 -5.82 1.9526
2024-07-26 2024-06-30 13F MERCK COM 58933Y105 960 -80,984 -98.83 9,753 -9.80 1.5718
2024-04-25 2024-03-31 13F MERCK COM 58933Y105 81,944 -1,486 -1.78 10,813 18.88 1.7915
2024-01-24 2023-12-31 13F MERCK COM 58933Y105 83,430 368 0.44 9,096 6.37 1.3297
2023-10-19 2023-09-30 13F MERCK COM 58933Y105 83,062 24,801 42.57 8,551 27.19 1.3289
2023-08-08 2023-06-30 13F MERCK COM 58933Y105 58,261 0 0.00 6,723 8.47 1.4945
2023-04-27 2023-03-31 13F MERCK COM 58933Y105 58,261 -3,000 -4.90 6,198 -8.81 1.4253
2023-01-26 2022-12-31 13F MERCK COM 58933Y105 61,261 -390 -0.63 6,797 28.03 1.5282
2022-10-13 2022-09-30 13F MERCK COM 58933Y105 61,651 -782 -1.25 5,309 -6.73 1.2738
2022-07-19 2022-06-30 13F MERCK COM 58933Y105 62,433 -69,347 -52.62 5,692 -47.36 1.2741
2022-04-21 2022-03-31 13F MERCK COM 58933Y105 131,780 -28,500 -17.78 10,813 -11.97 2.2755
2022-01-21 2021-12-31 13F MERCK COM 58933Y105 160,280 42,315 35.87 12,284 38.65 2.0265
2021-11-03 2021-09-30 13F MERCK COM 58933Y105 117,965 6,755 6.07 8,860 2.44 1.9260
2021-07-26 2021-06-30 13F MERCK COM 58933Y105 111,210 3,865 3.60 8,649 4.52 1.9474
2021-05-03 2021-03-31 13F MERCK & CO INC COM COM 58933Y105 107,345 -2,950 -2.67 8,275 -8.28 1.9328
2021-02-02 2020-12-31 13F MERCK & CO INC COM COM 58933Y105 110,295 220 0.20 9,022 -1.19 2.3708
2020-11-12 2020-09-30 13F MERCK & CO. COM 58933Y105 110,075 14,655 15.36 9,131 23.74 2.7796
2020-07-29 2020-06-30 13F MERCK & CO INC COM COM 58933Y105 95,420 57,571 152.11 7,379 153.40 2.2756
2020-05-13 2020-03-31 13F/A-1 MERCK & CO INC COM COM 58933Y105 37,849 14,140 59.64 2,912 35.06 0.9092
2020-05-05 2020-03-31 13F MERCK & CO INC COM COM 58933Y105 37,849 14,140 2,912 826,024.3042
2020-01-17 2019-12-31 13F MERCK & CO INC COM COM 58933Y105 23,709 0 0.00 2,156 8.02 0.5632
2019-11-12 2019-09-30 13F/A-1 MERCK COM 58933Y105 23,709 260 1.11 1,996 1.53 0.5573
2019-10-31 2019-09-30 13F MERCK & CO INC COM COM 58933Y105 23,709 260 1,996 0.5573
2019-08-01 2019-06-30 13F MERCK COM 58933Y105 23,449 0 0.00 1,966 0.82 0.5594
2019-05-13 2019-03-31 13F MERCK COM 58933Y105 23,449 0 0.00 1,950 8.82 0.5777
2019-02-12 2018-12-31 13F MERCK COM 58933Y105 23,449 -200 -0.85 1,792 6.79 0.4796
2018-11-27 2018-09-30 13F/A-2 MERCK COM 58933Y105 23,649 -75,620 -76.18 1,678 -72.15 0.4283
2018-11-15 2018-09-30 13F/A-1 MERCK COM 58933Y105 56,669 -42,600 4,020 0.7360
2018-11-10 2018-09-30 13F MERCK COM 58933Y105 56,669 -42,600 4,020 0.7381
2018-08-08 2018-06-30 13F MERCK COM 58933Y105 99,269 1,025 1.04 6,026 12.61 1.2529
2018-05-09 2018-03-31 13F MERCK COM 58933Y105 98,244 2,393 2.50 5,351 -0.80 1.1076
2018-02-09 2017-12-31 13F MERCK COM 58933Y105 95,851 41,112 75.11 5,394 53.89 1.1680
2017-11-07 2017-09-30 13F MERCK COM 58933Y105 54,739 -151 -0.28 3,505 -0.37 0.7900
2017-08-07 2017-06-30 13F MERCK COM 58933Y105 54,890 4,700 9.36 3,518 10.32 0.7643
2017-05-01 2017-03-31 13F MERCK COM 58933Y105 50,190 10,539 26.58 3,189 36.63 0.6555
2017-02-09 2016-12-31 13F MERCK COM 58933Y105 39,651 -3,800 -8.75 2,334 -13.94 0.4917
2016-11-15 2016-09-30 13F MERCK COM 58933Y105 43,451 7,300 20.19 2,712 30.20 0.6025
2016-08-12 2016-06-30 13F MERCK COM 58933Y105 36,151 -15,600 -30.14 2,083 -23.92 0.5032
2016-05-16 2016-03-31 13F/A-1 MERCK & CO INC COM 58933Y105 51,751 0 0.00 2,738 0.18 0.7176
2016-05-16 2016-03-31 13F MERCK & CO INC COM 58933Y105 4,760,012 4,708,261 89,964 0.6771
2016-02-08 2015-12-31 13F MERCK & CO INC COM 58933Y105 51,751 0 0.00 2,733 6.92 0.8117
2015-11-13 2015-09-30 13F MERCK & CO INC COM 58933Y105 51,751 3,400 7.03 2,556 -7.16 0.8839
2015-08-12 2015-06-30 13F MERCK & CO INC COM 58933Y105 48,351 -150 -0.31 2,753 -1.26 0.9072
2015-05-11 2015-03-31 13F MERCK & CO INC COM 58933Y105 48,501 4,300 9.73 2,788 11.08 0.9784
2015-02-11 2014-12-31 13F MERCK & CO INC COM 58933Y105 44,201 0 0.00 2,510 -4.20 1.0000
2014-11-14 2014-09-30 13F MERCK & CO INC COM 58933Y105 44,201 0 0.00 2,620 2.46 1.0899
2014-08-15 2014-06-30 13F MERCK & CO INC COM 58933Y105 44,201 0 0.00 2,557 1.91 1.0412
2014-05-16 2014-03-31 13F MERCK & CO INC COM 58933Y105 44,201 -127 -0.29 2,509 13.07 0.9851
2014-02-05 2013-12-31 13F MERCK & CO INC COM 58933Y105 44,328 0 0.00 2,219 5.17 1.0978
2013-11-14 2013-09-30 13F MERCK & CO INC COM 58933Y105 44,328 144 0.33 2,110 2.83 1.1220
2013-08-15 2013-06-30 13F MERCK & CO INC COM 58933Y105 44,184 44,184 2,052 1.1894
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.