Merck & Co., Inc.
MX ˙ BMV ˙ US58933Y1055
SecurityMX:MRK / Merck & Co., Inc.
InstitutionGreat Diamond Partners, LLC
Latest Disclosed Ownership8,476 shares
Latest Disclosed Value $ 1,019,578
Great Diamond Partners, LLC reports 1.78% decrease in ownership of MRK / Merck & Co., Inc.

On May 12, 2026 - Great Diamond Partners, LLC filed a 13F-HR form disclosing ownership of 8,476 shares of Merck & Co., Inc. (MX:MRK) valued at $1,019,578 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 6, 2026 disclosing 8,630 shares of Merck & Co., Inc.. This represents a change in shares of -1.78% 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)
2026-05-12 2026-03-31 13F MERCK COM 58933Y105 8,476 -154 -1.78 1,020 12.22 0.1963
2026-02-06 2025-12-31 13F MERCK COM 58933Y105 8,630 -629 -6.79 908 16.86 0.1748
2025-10-20 2025-09-30 13F MERCK COM 58933Y105 9,259 -26 -0.28 777 5.71 0.1507
2025-08-13 2025-06-30 13F MERCK COM 58933Y105 9,285 1,054 12.81 735 -0.41 0.1552
2025-05-13 2025-03-31 13F MERCK COM 58933Y105 8,231 -2,980 -26.58 739 -33.81 0.2020
2025-01-23 2024-12-31 13F MERCK COM 58933Y105 11,211 -1,451 -11.46 1,115 -22.41 0.2884
2024-10-25 2024-09-30 13F MERCK COM 58933Y105 12,662 -7,114 -35.97 1,438 -41.30 0.3653
2024-07-29 2024-06-30 13F MERCK COM 58933Y105 19,776 -1,502 -7.06 2,448 -12.79 0.5753
2024-05-08 2024-03-31 13F MERCK COM 58933Y105 21,278 387 1.85 2,808 23.28 0.6447
2024-02-07 2023-12-31 13F MERCK COM 58933Y105 20,891 323 1.57 2,277 7.56 0.5613
2023-10-19 2023-09-30 13F MERCK COM 58933Y105 20,568 -588 -2.78 2,117 -13.27 0.5733
2023-07-17 2023-06-30 13F MERCK COM 58933Y105 21,156 4,029 23.52 2,441 33.97 0.6445
2023-05-04 2023-03-31 13F MERCK COM 58933Y105 17,127 58 0.34 1,822 -3.75 0.5277
2023-02-01 2022-12-31 13F MERCK COM 58933Y105 17,069 -237 -1.37 1,894 27.05 0.5830
2022-10-24 2022-09-30 13F MERCK & CO INC COM COM 58933Y105 17,306 12 0.07 1,490 -5.46 0.5092
2022-07-26 2022-06-30 13F MERCK & CO INC COM COM 58933Y105 17,294 428 2.54 1,576 13.96 0.5239
2022-05-05 2022-03-31 13F MERCK & CO INC COM COM 58933Y105 16,866 1,563 10.21 1,383 18.00 0.3849
2022-01-26 2021-12-31 13F MERCK & CO INC COM COM 58933Y105 15,303 -1,008 -6.18 1,172 -4.33 0.3018
2021-10-21 2021-09-30 13F MERCK & CO INC COM COM 58933Y105 16,311 -3 -0.02 1,225 -3.39 0.3358
2021-07-26 2021-06-30 13F MERCK & CO INC COM COM 58933Y105 16,314 -116 -0.71 1,268 0.16 0.3586
2021-05-04 2021-03-31 13F MERCK & CO. INC COM COM 58933Y105 16,430 -1,282 -7.24 1,266 -12.57 0.3895
2021-01-26 2020-12-31 13F MERCK & CO. INC COM COM 58933Y105 17,712 -11,397 -39.15 1,448 -40.02 0.4616
2020-10-19 2020-09-30 13F MERCK & CO. INC COM COM 58933Y105 29,109 965 3.43 2,414 10.94 0.8858
2020-08-04 2020-06-30 13F MERCK & CO. INC COM COM 58933Y105 28,144 -2,456 -8.03 2,176 -7.56 0.9008
2020-05-01 2020-03-31 13F MERCK & CO. INC COM COM 58933Y105 30,600 12,091 65.32 2,354 39.87 1.2118
2020-02-07 2019-12-31 13F MERCK & CO INC COM COM 58933Y105 18,509 18,509 1,683 0.6400
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.