Merck & Co., Inc.
MX ˙ BMV ˙ US58933Y1055
SecurityMX:MRK / Merck & Co., Inc.
InstitutionRafferty Asset Management, LLC
Latest Disclosed Ownership193,053 shares
Latest Disclosed Value $ 23,222,345
Rafferty Asset Management, LLC reports 28.40% decrease in ownership of MRK / Merck & Co., Inc.

On May 15, 2026 - Rafferty Asset Management, LLC filed a 13F-HR form disclosing ownership of 193,053 shares of Merck & Co., Inc. (MX:MRK) valued at $23,222,345 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 13, 2026 disclosing 269,620 shares of Merck & Co., Inc.. This represents a change in shares of -28.40% 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)
2026-05-15 2026-03-31 13F MERCK COM 58933Y105 193,053 -76,567 -28.40 23,222 -18.17 0.0943
2026-02-13 2025-12-31 13F MERCK COM 58933Y105 269,620 -10,228 -3.65 28,380 20.83 0.0980
2025-11-12 2025-09-30 13F MERCK COM 58933Y105 279,848 11,466 4.27 23,488 10.55 0.0762
2025-08-14 2025-06-30 13F MERCK COM 58933Y105 268,382 30,670 12.90 21,245 -0.43 0.0701
2025-05-14 2025-03-31 13F MERCK COM 58933Y105 237,712 -52,722 -18.15 21,337 -26.15 0.0910
2025-02-14 2024-12-31 13F MERCK COM 58933Y105 290,434 29,554 11.33 28,892 -2.47 0.1022
2024-11-13 2024-09-30 13F MERCK COM 58933Y105 260,880 -17,704 -6.35 29,626 -14.10 0.1015
2024-08-13 2024-06-30 13F MERCK COM 58933Y105 278,584 12,966 4.88 34,489 -1.60 0.1280
2024-05-13 2024-03-31 13F MERCK COM 58933Y105 265,618 3,715 1.42 35,048 22.75 0.1307
2024-02-13 2023-12-31 13F MERCK COM 58933Y105 261,903 -6,258 -2.33 28,553 3.42 0.1204
2023-11-13 2023-09-30 13F MERCK COM 58933Y105 268,161 19,769 7.96 27,607 -3.68 0.1623
2023-08-11 2023-06-30 13F MERCK COM 58933Y105 248,392 19,079 8.32 28,662 17.48 0.1616
2023-05-11 2023-03-31 13F MERCK COM 58933Y105 229,313 8,481 3.84 24,397 -0.43 0.1653
2023-02-13 2022-12-31 13F MERCK COM 58933Y105 220,832 82,454 59.59 24,501 105.60 0.2051
2022-11-14 2022-09-30 13F MERCK COM 58933Y105 138,378 74,303 115.96 11,917 103.99 0.1268
2022-08-12 2022-06-30 13F MERCK COM 58933Y105 64,075 -18,716 -22.61 5,842 -14.00 0.0538
2022-05-13 2022-03-31 13F MERCK COM 58933Y105 82,791 -14,037 -14.50 6,793 -8.46 0.0403
2022-02-10 2021-12-31 13F MERCK COM 58933Y105 96,828 5,685 6.24 7,421 8.40 0.0391
2021-11-10 2021-09-30 13F MERCK COM 58933Y105 91,143 32,475 55.35 6,846 50.03 0.0468
2021-08-10 2021-06-30 13F MERCK COM 58933Y105 58,668 2,328 4.13 4,563 5.07 0.0287
2021-05-10 2021-03-31 13F MERCK & CO. COM 58933Y105 56,340 3,685 7.00 4,343 0.84 0.0297
2021-02-10 2020-12-31 13F MERCK & CO. COM 58933Y105 52,655 -2,039 -3.73 4,307 -5.07 0.0421
2020-11-13 2020-09-30 13F MERCK & CO. COM 58933Y105 54,694 -11,485 -17.35 4,537 -11.35 0.0549
2020-08-07 2020-06-30 13F MERCK & CO. COM 58933Y105 66,179 40,234 155.07 5,118 156.41 0.0721
2020-05-15 2020-03-31 13F MERCK & CO. COM 58933Y105 25,945 -64,681 -71.37 1,996 -75.78 0.0836
2020-02-10 2019-12-31 13F MERCK COM 58933Y105 90,626 58,934 185.96 8,242 208.92 0.1268
2019-11-14 2019-09-30 13F MERCK COM 58933Y105 31,692 -2,255 -6.64 2,668 -6.25 0.0417
2019-08-09 2019-06-30 13F MERCK COM 58933Y105 33,947 27,649 439.01 2,846 443.13 0.0500
2019-05-15 2019-03-31 13F MERCK COM 58933Y105 6,298 6,298 524 0.0084
2019-02-11 2018-12-31 13F MERCK COM 58933Y105 0 -2,953 -100.00 0 -100.00
2018-11-09 2018-09-30 13F MERCK COM 58933Y105 2,953 2,953 209 0.0032
2017-08-11 2017-06-30 13F MERCK COM 58933Y105 0 -7,019 -100.00 0 -100.00
2017-05-11 2017-03-31 13F MERCK COM 58933Y105 7,019 7,019 446 0.0098
2016-05-12 2016-03-31 13F MERCK & CO INC COM 58933Y105 0 0 0 0.0000
2016-02-12 2015-12-31 13F MERCK & CO INC COM 58933Y105 0 0 0 0.0000
2015-11-12 2015-09-30 13F MERCK & CO INC COM 58933Y105 0 -5,562 -100.00 0 -100.00
2015-08-12 2015-06-30 13F MERCK & CO INC COM 58933Y105 5,562 -159 -2.78 317 -3.65 0.0213
2015-05-14 2015-03-31 13F MERCK & CO INC COM 58933Y105 5,721 5,721 329 0.0248
2015-02-13 2014-12-31 13F MERCK & CO INC COM 58933Y105 0 -6,344 -100.00 0 -100.00
2014-11-14 2014-09-30 13F MERCK & CO INC COM 58933Y105 6,344 2,388 60.36 376 64.19 0.0405
2014-08-13 2014-06-30 13F MERCK & CO INC COM 58933Y105 3,956 -13 -0.33 229 1.78 0.0440
2014-05-14 2014-03-31 13F MERCK & CO INC COM 58933Y105 3,969 3,969 225 0.0466
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.