Merck & Co., Inc.
MX ˙ BMV ˙ US58933Y1055
SecurityMX:MRK / Merck & Co., Inc.
InstitutionRobeco Institutional Asset Management B.V.
Latest Disclosed Ownership2,322,293 shares
Latest Disclosed Value $ 279,348,626
Robeco Institutional Asset Management B.V. reports 7.03% decrease in ownership of MRK / Merck & Co., Inc.

On April 21, 2026 - Robeco Institutional Asset Management B.V. filed a 13F-HR form disclosing ownership of 2,322,293 shares of Merck & Co., Inc. (MX:MRK) valued at $279,348,626 USD as of March 31, 2026. The entity filed a previous 13F-HR on January 23, 2026 disclosing 2,497,975 shares of Merck & Co., Inc.. This represents a change in shares of -7.03% 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)
2026-04-21 2026-03-31 13F MERCK COM 58933Y105 2,322,293 -175,682 -7.03 279,349 6.24 0.3982
2026-01-23 2025-12-31 13F MERCK COM 58933Y105 2,497,975 -508,157 -16.90 262,937 4.21 0.3745
2025-10-22 2025-09-30 13F MERCK COM 58933Y105 3,006,132 -157,285 -4.97 252,305 0.75 0.3655
2025-07-18 2025-06-30 13F MERCK COM 58933Y105 3,163,417 556,891 21.37 250,416 7.03 0.4049
2025-04-23 2025-03-31 13F MERCK COM 58933Y105 2,606,526 -50,885 -1.91 233,962 -11.50 0.4545
2025-01-23 2024-12-31 13F MERCK COM 58933Y105 2,657,411 -546,267 -17.05 264,359 -27.34 0.5011
2024-10-29 2024-09-30 13F MERCK COM 58933Y105 3,203,678 -103,129 -3.12 363,810 -11.13 0.7227
2024-07-23 2024-06-30 13F MERCK COM 58933Y105 3,306,807 378,024 12.91 409,383 5.93 0.8808
2024-04-24 2024-03-31 13F MERCK COM 58933Y105 2,928,783 -15,248 -0.52 386,453 20.41 0.8398
2024-02-14 2023-12-31 13F/A-1 MERCK COM 58933Y105 2,944,031 -204,777 -6.50 320,958 -0.99 0.7781
2024-02-08 2023-12-31 13F MERCK COM 58933Y105 1,580,726 -1,568,082 2,944 0.5514
2023-10-24 2023-09-30 13F MERCK COM 58933Y105 3,148,808 87,972 2.87 324,170 -8.22 0.8663
2023-07-24 2023-06-30 13F MERCK COM 58933Y105 3,060,836 -255,374 -7.70 353,190 0.11 0.9260
2023-05-04 2023-03-31 13F MERCK COM 58933Y105 3,316,210 -301,558 -8.34 352,812 -12.10 0.9618
2023-02-07 2022-12-31 13F MERCK COM 58933Y105 3,617,768 -430,359 -10.63 401,391 15.14 1.1567
2022-12-01 2022-09-30 13F/A-1 MERCK COM 58933Y105 4,048,127 -51,494 -1.26 348,624 -6.73 1.1266
2022-10-27 2022-09-30 13F MERCK COM 58933Y105 4,048,127 -51,494 348,624 1.1115
2022-12-01 2022-06-30 13F/A-1 MERCK COM 58933Y105 4,099,621 305,247 8.04 373,761 20.05 1.1613
2022-07-27 2022-06-30 13F MERCK COM 58933Y105 4,099,621 305,247 373,761 1.1450
2022-12-01 2022-03-31 13F/A-1 MERCK COM 58933Y105 3,794,374 -1,329,017 -25.94 311,332 -20.71 0.7333
2022-04-26 2022-03-31 13F MERCK COM 58933Y105 3,794,374 -1,329,017 311,332 0.7245
2022-12-01 2021-12-31 13F/A-1 MERCK COM 58933Y105 5,123,391 791,320 18.27 392,659 20.67 0.8357
2022-01-31 2021-12-31 13F MERCK COM 58933Y105 5,123,391 791,320 392,659 0.8253
2022-12-01 2021-09-30 13F/A-1 MERCK COM 58933Y105 4,332,071 -104,587 -2.36 325,387 -5.70 0.7214
2021-10-20 2021-09-30 13F MERCK COM 58933Y105 4,332,071 -104,587 325,387 0.7122
2022-12-01 2021-06-30 13F/A-1 MERCK COM 58933Y105 4,436,658 -64,548 -1.43 345,037 -0.57 0.7648
2021-07-28 2021-06-30 13F MERCK COM 58933Y105 4,436,658 -64,548 345,037 0.7544
2022-12-01 2021-03-31 13F/A-1 MERCK & CO. COM 58933Y105 4,501,206 318,686 7.62 347,004 1.42 0.8552
2021-04-23 2021-03-31 13F MERCK & CO. COM 58933Y105 4,501,206 318,686 347,004 0.8432
2022-12-01 2020-12-31 13F/A-1 MERCK & CO. COM 58933Y105 4,182,520 661,388 18.78 342,130 17.14 0.8990
2021-01-28 2020-12-31 13F MERCK & CO. COM 58933Y105 4,182,520 661,388 342,130 0.8882
2021-01-19 2020-09-30 13F/A-1 MERCK & CO. COM 58933Y105 3,521,132 78,155 2.27 292,079 9.70 0.9028
2020-10-29 2020-09-30 13F MERCK & CO. COM 58933Y105 3,527,862 75,599 292,637 903,758.2975
2021-01-19 2020-06-30 13F/A-1 MERCK & CO. COM 58933Y105 3,442,977 -609,919 -15.05 266,246 -14.62 0.9042
2020-07-20 2020-06-30 13F MERCK & CO. COM 58933Y105 3,452,263 -610,667 266,964 905,856.4698
2021-01-19 2020-03-31 13F/A-1 MERCK & CO. COM 58933Y105 4,052,896 -13,966 -0.34 311,826 -15.70 1.2509
2020-04-30 2020-03-31 13F MERCK & CO. COM 58933Y105 4,062,930 -3,932 312,598 1,252,963.2811
2021-01-19 2019-12-31 13F/A-1 MERCK COM 58933Y105 4,066,862 119,207 3.02 369,885 11.30 1.1842
2020-02-06 2019-12-31 13F MERCK COM 58933Y105 4,066,862 119,207 369,885 1,183,048.7286
2021-01-19 2019-09-30 13F/A-1 MERCK COM 58933Y105 3,947,655 -59,004 -1.47 332,317 -1.08 1.1732
2019-10-17 2019-09-30 13F MERCK COM 58933Y105 3,947,655 -59,004 332,317 1,171,554.0912
2021-01-19 2019-06-30 13F/A-1 MERCK COM 58933Y105 4,006,659 172,407 4.50 335,961 5.35 1.1864
2019-07-19 2019-06-30 13F MERCK COM 58933Y105 4,006,659 172,407 335,961 1,184,686.3628
2021-01-19 2019-03-31 13F/A-1 MERCK COM 58933Y105 3,834,252 709,780 22.72 318,897 33.66 1.1727
2019-05-02 2019-03-31 13F MERCK COM 58933Y105 3,834,252 709,780 318,897 1,170,876.3414
2021-01-19 2018-12-31 13F/A-1 MERCK COM 58933Y105 3,124,472 680,339 27.84 238,581 37.59 1.0713
2019-02-08 2018-12-31 13F MERCK COM 58933Y105 3,124,472 680,339 238,581 1,069,427.5095
2021-01-19 2018-09-30 13F/A-1 MERCK COM 58933Y105 2,444,133 131,077 5.67 173,399 23.49 0.6867
2018-10-25 2018-09-30 13F MERCK COM 58933Y105 2,440,341 127,285 173,130
2021-01-19 2018-06-30 13F/A-1 MERCK COM 58933Y105 2,313,056 -66,848 -2.81 140,417 8.31 0.6396
2018-08-03 2018-06-30 13F MERCK COM 58933Y105 2,313,056 -66,848 140,417
2021-01-19 2018-03-31 13F/A-1 MERCK COM 58933Y105 2,379,904 81,493 3.55 129,645 0.23 0.6083
2018-05-07 2018-03-31 13F MERCK COM 58933Y105 2,379,904 68,475 129,645 606,289.0192
2021-01-19 2017-12-31 13F/A-1 MERCK COM 58933Y105 2,298,411 277,798 13.75 129,348 -0.02 0.6703
2018-01-25 2017-12-31 13F MERCK COM 58933Y105 2,311,429 265,898 130,081
2021-01-19 2017-09-30 13F/A-1 MERCK COM 58933Y105 2,020,613 -7,345 -0.36 129,377 -0.46 0.8034
2017-10-17 2017-09-30 13F MERCK COM 58933Y105 2,045,531 -5,702 130,972 811,417.4864
2021-01-19 2017-06-30 13F/A-1 MERCK COM 58933Y105 2,027,958 58,138 2.95 129,973 3.84 0.8372
2017-08-07 2017-06-30 13F MERCK COM 58933Y105 2,051,233 51,828 131,465 855,943.0273
2021-01-19 2017-03-31 13F/A-1 MERCK COM 58933Y105 1,969,820 110,682 5.95 125,162 14.36 0.8334
2017-05-15 2017-03-31 13F MERCK COM 58933Y105 1,999,405 140,267 127,042 843,805.2921
2017-02-09 2016-12-31 13F MERCK COM 58933Y105 1,859,138 804,753 76.32 109,449 66.32 0.8562
2016-11-07 2016-09-30 13F MERCK COM 58933Y105 1,054,385 414,883 64.88 65,805 78.61 0.4864
2016-07-22 2016-06-30 13F MERCK COM 58933Y105 639,502 12,875 2.05 36,842 11.12 0.2794
2016-05-16 2016-03-31 13F MERCK & CO INC COM 58933Y105 626,627 5,136 0.83 33,154 1.00 0.2660
2016-02-08 2015-12-31 13F MERCK & CO INC COM 58933Y105 621,491 -1,108,486 -64.08 32,826 -61.58 0.2807
2015-11-12 2015-09-30 13F MERCK & CO INC COM 58933Y105 1,729,977 67,492 4.06 85,444 -9.72 0.6509
2015-08-17 2015-06-30 13F MERCK & CO INC COM 58933Y105 1,662,485 -68,428 -3.95 94,643 -4.87 0.7184
2015-04-24 2015-03-31 13F MERCK & CO INC COM 58933Y105 1,730,913 1,083,047 167.17 99,491 170.41 0.7480
2015-02-12 2014-12-31 13F MERCK & CO INC COM 58933Y105 647,866 137,408 26.92 36,793 21.59 0.2638
2014-11-10 2014-09-30 13F MERCK & CO INC COM 58933Y105 510,458 140,051 37.81 30,260 41.20 0.2162
2014-08-13 2014-06-30 13F MERCK & CO INC COM 58933Y105 370,407 85,356 29.94 21,430 32.41 0.1534
2014-05-07 2014-03-31 13F MERCK & CO INC COM 58933Y105 285,051 16,819 6.27 16,184 20.56 0.1242
2014-02-04 2013-12-31 13F MERCK & CO INC COM 58933Y105 268,232 31,540 13.33 13,424 19.13 0.1115
2013-11-12 2013-09-30 13F MERCK & CO INC COM 58933Y105 236,692 10,575 4.68 11,268 7.27 0.1095
2013-08-27 2013-06-30 13F Merck COM 58933Y105 226,117 226,117 10,504 0.1063
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.