Merck & Co., Inc.
MX ˙ BMV ˙ US58933Y1055
SecurityMX:MRK / Merck & Co., Inc.
InstitutionBlair William & Co/il
Latest Disclosed Ownership901,789 shares
Latest Disclosed Value $ 108,476,224
Blair William & Co/il reports 8.13% increase in ownership of MRK / Merck & Co., Inc.

On May 8, 2026 - Blair William & Co/il filed a 13F-HR form disclosing ownership of 901,789 shares of Merck & Co., Inc. (MX:MRK) valued at $108,476,224 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 17, 2026 disclosing 834,024 shares of Merck & Co., Inc.. This represents a change in shares of 8.13% 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)
2026-05-08 2026-03-31 13F MERCK COM 58933Y105 901,789 67,765 8.13 108,476 23.56 0.3109
2026-02-17 2025-12-31 13F MERCK COM 58933Y105 834,024 21,658 2.67 87,789 28.76 0.2356
2025-11-12 2025-09-30 13F MERCK COM 58933Y105 812,366 -60,101 -6.89 68,182 -1.28 0.1815
2025-07-24 2025-06-30 13F MERCK COM 58933Y105 872,467 -68,932 -7.32 69,064 -18.27 0.1918
2025-05-09 2025-03-31 13F MERCK COM 58933Y105 941,399 -67,564 -6.70 84,500 -15.81 0.2548
2025-02-12 2024-12-31 13F MERCK COM 58933Y105 1,008,963 6,634 0.66 100,372 -11.82 0.2920
2024-11-12 2024-09-30 13F MERCK COM 58933Y105 1,002,329 3,558 0.36 113,824 -7.94 0.3343
2024-08-12 2024-06-30 13F MERCK COM 58933Y105 998,771 260,742 35.33 123,648 26.97 0.3814
2024-05-09 2024-03-31 13F MERCK COM 58933Y105 738,029 313 0.04 97,383 21.08 0.3059
2024-02-12 2023-12-31 13F MERCK COM 58933Y105 737,716 15,121 2.09 80,426 8.11 0.2741
2023-11-09 2023-09-30 13F MERCK COM 58933Y105 722,595 4,288 0.60 74,391 -10.25 0.2853
2023-08-11 2023-06-30 13F MERCK COM 58933Y105 718,307 16,435 2.34 82,885 11.00 0.3036
2023-05-12 2023-03-31 13F MERCK COM 58933Y105 701,872 6,275 0.90 74,672 -3.24 0.2983
2023-02-10 2022-12-31 13F MERCK COM 58933Y105 695,597 10,461 1.53 77,177 30.80 0.3356
2022-11-09 2022-09-30 13F MERCK COM 58933Y105 685,136 43,408 6.76 59,004 0.85 0.2710
2022-08-10 2022-06-30 13F MERCK COM 58933Y105 641,728 2,436 0.38 58,506 11.54 0.2596
2022-05-13 2022-03-31 13F MERCK COM 58933Y105 639,292 -84,408 -11.66 52,454 -5.43 0.1839
2022-02-14 2021-12-31 13F MERCK COM 58933Y105 723,700 42,370 6.22 55,464 8.38 0.1740
2021-11-12 2021-09-30 13F MERCK COM 58933Y105 681,330 55,013 8.78 51,175 5.06 0.1742
2021-08-12 2021-06-30 13F MERCK COM 58933Y105 626,317 -10,005 -1.57 48,709 -0.70 0.1688
2021-05-13 2021-03-31 13F MERCK & CO. COM 58933Y105 636,322 -30,458 -4.57 49,054 -10.06 0.1851
2021-02-09 2020-12-31 13F MERCK & CO. COM 58933Y105 666,780 79,779 13.59 54,543 12.02 0.2000
2020-11-06 2020-09-30 13F MERCK & CO. COM 58933Y105 587,001 77,638 15.24 48,692 23.62 0.2065
2020-08-12 2020-06-30 13F MERCK & CO. COM 58933Y105 509,363 19,932 4.07 39,389 4.60 0.1878
2020-05-11 2020-03-31 13F MERCK & CO. COM 58933Y105 489,431 -44,905 -8.40 37,657 -22.51 0.2354
2020-02-13 2019-12-31 13F MERCK COM 58933Y105 534,336 -16,871 -3.06 48,598 4.73 0.2498
2019-11-12 2019-09-30 13F MERCK COM 58933Y105 551,207 27,973 5.35 46,401 5.76 0.2674
2019-08-13 2019-06-30 13F MERCK COM 58933Y105 523,234 45,755 9.58 43,873 10.48 0.2509
2019-05-14 2019-03-31 13F MERCK COM 58933Y105 477,479 52,106 12.25 39,712 22.18 0.2421
2019-02-14 2018-12-31 13F MERCK COM 58933Y105 425,373 14,763 3.60 32,503 11.58 0.2374
2018-11-13 2018-09-30 13F MERCK COM 58933Y105 410,610 2,579 0.63 29,129 17.61 0.1785
2018-08-13 2018-06-30 13F MERCK COM 58933Y105 408,031 -1,296 -0.32 24,767 11.08 0.1684
2018-05-15 2018-03-31 13F MERCK COM 58933Y105 409,327 -21,474 -4.98 22,296 -8.02 0.1577
2018-02-14 2017-12-31 13F MERCK COM 58933Y105 430,801 1,186 0.28 24,241 -11.88 0.1646
2017-11-13 2017-09-30 13F MERCK COM 58933Y105 429,615 10,084 2.40 27,508 2.31 0.2063
2017-08-04 2017-06-30 13F MERCK COM 58933Y105 419,531 80,431 23.72 26,888 22.03 0.2019
2017-05-10 2017-03-31 13F MERCK COM 58933Y105 339,100 14,906 4.60 22,034 15.45 0.1776
2017-02-14 2016-12-31 13F MERCK COM 58933Y105 324,194 2,540 0.79 19,085 -4.93 0.1707
2016-11-14 2016-09-30 13F MERCK COM 58933Y105 321,654 10,778 3.47 20,074 12.08 0.1774
2016-08-08 2016-06-30 13F MERCK COM 58933Y105 310,876 1,019 0.33 17,910 9.25 0.1670
2016-05-16 2016-03-31 13F MERCK COM 58933Y105 309,857 -22,548 -6.78 16,394 -6.62 0.1543
2016-02-16 2015-12-31 13F MERCK COM 58933Y105 332,405 24,245 7.87 17,557 15.35 0.1648
2015-11-12 2015-09-30 13F MERCK COM 58933Y105 308,160 5,286 1.75 15,220 -11.73 0.1317
2015-08-03 2015-06-30 13F MERCK COM 58933Y105 302,874 8,211 2.79 17,242 1.81 0.0258
2015-05-11 2015-03-31 13F MERCK COM 58933Y105 294,663 294,663 0.00 16,936 0.0261
2015-02-05 2014-12-31 13F MERCK COM 58933Y105 0 -272,017 -100.00 0 -100.00
2014-11-04 2014-09-30 13F MERCK COM 58933Y105 272,017 821 0.30 16,125 2.79 0.0276
2014-08-01 2014-06-30 13F MERCK COM 58933Y105 271,196 -22,687 -7.72 15,688 -5.96 0.0256
2014-05-06 2014-03-31 13F MERCK COM 58933Y105 293,883 46,915 19.00 16,683 34.98 0.0276
2014-02-11 2013-12-31 13F MERCK COM 58933Y105 246,968 -55,172 -18.26 12,360 -14.07 0.0204
2013-11-12 2013-09-30 13F MERCK COM 58933Y105 302,140 -5,096 -1.66 14,384 0.79 0.0256
2013-08-07 2013-06-30 13F MERCK COM 58933Y105 307,236 307,236 14,271 0.0282
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.