Merck & Co., Inc.
CH ˙ SWX ˙ US58933Y1055
SecurityCH:MRK / Merck & Co., Inc.
InstitutionBoston Partners
Latest Disclosed Ownership641,766 shares
Latest Disclosed Value $ 77,505,813
Boston Partners reports 4.03% decrease in ownership of MRK / Merck & Co., Inc.

On May 11, 2026 - Boston Partners filed a 13F-HR form disclosing ownership of 641,766 shares of Merck & Co., Inc. (CH:MRK) valued at $77,505,813 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 13, 2026 disclosing 668,722 shares of Merck & Co., Inc.. This represents a change in shares of -4.03% 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 MERCK COM 58933Y105 641,766 -26,956 -4.03 77,506 10.07 0.0347
2026-02-13 2025-12-31 13F MERCK COM 58933Y105 668,722 -34,160 -4.86 70,413 19.32 0.0729
2025-11-13 2025-09-30 13F MERCK COM 58933Y105 702,882 -61,111 -8.00 59,012 -2.44 0.0606
2025-08-12 2025-06-30 13F/A-1 MERCK COM 58933Y105 763,993 -9,142 -1.18 60,490 -12.78 0.0672
2025-08-07 2025-06-30 13F MERCK COM 58933Y105 761,105 -12,030 60,262 0.0277
2025-05-13 2025-03-31 13F MERCK COM 58933Y105 773,135 -3,658 -0.47 69,351 -10.23 0.0839
2025-02-11 2024-12-31 13F MERCK COM 58933Y105 776,793 -436,367 -35.97 77,256 -43.90 0.0940
2024-11-12 2024-09-30 13F MERCK COM 58933Y105 1,213,160 -7,931 -0.65 137,702 -8.93 0.1625
2024-08-14 2024-06-30 13F MERCK COM 58933Y105 1,221,091 -39,489 -3.13 151,206 -9.09 0.1878
2024-05-28 2024-03-31 13F/A-1 MERCK COM 58933Y105 1,260,580 -34,684 -2.68 166,327 17.72 0.1981
2024-05-13 2024-03-31 13F MERCK COM 58933Y105 1,260,580 -34,684 166,327 0.0823
2024-02-07 2023-12-31 13F MERCK COM 58933Y105 1,295,264 -95,976 -6.90 141,293 -1.35 0.1871
2023-11-08 2023-09-30 13F MERCK COM 58933Y105 1,391,240 -52,937 -3.67 143,226 -14.01 0.1983
2023-08-10 2023-06-30 13F MERCK COM 58933Y105 1,444,177 -133,036 -8.43 166,558 -0.79 0.2242
2023-05-09 2023-03-31 13F MERCK COM 58933Y105 1,577,213 -36,290 -2.25 167,882 -6.20 0.2308
2023-02-08 2022-12-31 13F MERCK COM 58933Y105 1,613,503 -101,192 -5.90 178,985 21.12 0.2421
2022-11-09 2022-09-30 13F MERCK COM 58933Y105 1,714,695 -101,950 -5.61 147,779 -10.76 0.2163
2022-08-10 2022-06-30 13F MERCK COM 58933Y105 1,816,645 -68,838 -3.65 165,601 7.02 0.2314
2022-05-10 2022-03-31 13F MERCK COM 58933Y105 1,885,483 -57,297 -2.95 154,744 3.92 0.1875
2022-02-04 2021-12-31 13F MERCK COM 58933Y105 1,942,780 -846,752 -30.35 148,914 -28.95 0.1794
2021-11-05 2021-09-30 13F MERCK COM 58933Y105 2,789,532 151,945 5.76 209,584 2.17 0.2655
2021-08-12 2021-06-30 13F MERCK COM 58933Y105 2,637,587 155,564 6.27 205,132 7.20 0.2616
2021-05-10 2021-03-31 13F MERCK & CO. COM 58933Y105 2,482,023 730,354 41.69 191,347 33.54 0.2566
2021-02-10 2020-12-31 13F/A-1 MERCK & CO. COM 58933Y105 1,751,669 -3,057,918 -63.58 143,286 -64.08 0.2228
2021-02-04 2020-12-31 13F MERCK & CO. COM 58933Y105 1,751,669 -3,057,918 143,286 85,963.0833
2020-11-13 2020-09-30 13F/A-1 MERCK & CO. COM 58933Y105 4,809,587 -495,221 -9.34 398,956 -2.76 0.7265
2020-11-09 2020-09-30 13F MERCK & CO. COM 58933Y105 5,304,808 0 410,292 301,203.2029
2020-08-12 2020-06-30 13F MERCK & CO. COM 58933Y105 5,304,808 -1,128,343 -17.54 410,292 -17.08 0.7536
2020-05-13 2020-03-31 13F MERCK & CO. COM 58933Y105 6,433,151 3,415,065 113.15 494,790 80.24 0.9826
2020-02-06 2019-12-31 13F/A-1 MERCK COM 58933Y105 3,018,086 -428,054 -12.42 274,521 -5.37 0.3631
2020-02-05 2019-12-31 13F MERCK COM 58933Y105 3,018,086 -428,054 274,521 154,343.7241
2019-11-20 2019-09-30 13F/A-1 MERCK COM 58933Y105 3,446,140 -177,728 -4.90 290,114 -4.50 0.3929
2019-11-08 2019-09-30 13F MERCK COM 58933Y105 3,624,635 767 303,952 0.4020
2019-08-26 2019-06-30 13F/A-1 MERCK COM 58933Y105 3,623,868 -180,447 -4.74 303,796 -3.99 0.3984
2019-08-09 2019-06-30 13F MERCK COM 58933Y105 3,623,868 -180,447 303,796
2019-05-13 2019-03-31 13F/A-1 MERCK COM 58933Y105 3,804,315 -127,761 -3.25 316,405 5.31 0.4192
2019-05-03 2019-03-31 13F MERCK COM 58933Y105 3,804,315 -127,761 316,405
2019-02-07 2018-12-31 13F MERCK COM 58933Y105 3,932,076 -9,482,253 -70.69 300,450 -68.43 0.4317
2018-11-14 2018-09-30 13F MERCK COM 58933Y105 13,414,329 -1,135,296 -7.80 951,612 7.75 1.1058
2018-08-03 2018-06-30 13F MERCK COM 58933Y105 14,549,625 -372,072 -2.49 883,163 8.66 1.0585
2018-05-04 2018-03-31 13F MERCK COM 58933Y105 14,921,697 -2,242,131 -13.06 812,785 -15.84 0.9800
2018-02-14 2017-12-31 13F/A-1 MERCK COM 58933Y105 17,163,828 -1,567,046 -8.37 965,808 -19.47 1.1378
2018-02-01 2017-12-31 13F MERCK COM 58933Y105 17,163,828 -1,567,046 965,808
2017-11-02 2017-09-30 13F MERCK COM 58933Y105 18,730,874 145,744 0.78 1,199,338 0.69 1.4819
2017-08-02 2017-06-30 13F MERCK COM 58933Y105 18,585,130 -1,349,886 -6.77 1,191,121 -5.96 1.5147
2017-05-03 2017-03-31 13F MERCK COM 58933Y105 19,935,016 500,476 2.58 1,266,671 10.71 1.6174
2017-02-06 2016-12-31 13F MERCK COM 58933Y105 19,434,540 969,760 5.25 1,144,111 -0.72 1.5044
2016-11-09 2016-09-30 13F MERCK COM 58933Y105 18,464,780 -569,519 -2.99 1,152,387 5.09 1.6113
2016-08-05 2016-06-30 13F MERCK COM 58933Y105 19,034,299 3,655,639 23.77 1,096,566 34.77 1.5844
2016-05-12 2016-03-31 13F MERCK & CO INC COM 58933Y105 15,378,660 747,479 5.11 813,685 5.29 1.1985
2016-02-08 2015-12-31 13F MERCK & CO INC COM 58933Y105 14,631,181 -2,019,328 -12.13 772,819 -6.03 1.1070
2015-11-10 2015-09-30 13F MERCK & CO INC COM 58933Y105 16,650,509 1,739,003 11.66 822,369 -3.13 1.2535
2015-08-10 2015-06-30 13F MERCK & CO INC COM 58933Y105 14,911,506 753,952 5.33 848,911 4.32 1.2195
2015-05-05 2015-03-31 13F MERCK & CO INC COM 58933Y105 14,157,554 14,157,554 813,776 1.2115
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.