Merck & Co., Inc.
MX ˙ BMV ˙ US58933Y1055
SecurityMX:MRK / Merck & Co., Inc.
InstitutionRossmore Private Capital
Latest Disclosed Ownership57,421 shares
Latest Disclosed Value $ 6,955,989
Rossmore Private Capital ownership in MRK / Merck & Co., Inc.

On May 1, 2026 - Rossmore Private Capital filed a 13F-HR form disclosing ownership of 57,421 shares of Merck & Co., Inc. (MX:MRK) valued at $6,955,989 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 5, 2026 disclosing 67,082 shares of Merck & Co., Inc.. This represents a change in shares of -14.40% during the quarter.

Rossmore Private Capital has a history of taking positions in derivatives of the underlying security (MRK) in the form of stock options.

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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Institutional Put/Call Ratios
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In addition to reporting standard equity and debt issues, institutions with more than 100MM assets under management must also disclose their put and call option holdings. Since put options generally indicate negative sentiment, and call options indicate positive sentiment, we can get a sense of the overall institutional sentiment by plotting the ratio of puts to calls. The chart to the right plots the historical put/call ratio for this instrument.

Using Put/Call Ratio as an indicator of investor sentiment overcomes one of the key deficiencies of using total institutional ownership, which is that a significant amount of assets under management are invested passively to track indices. Passively-managed funds do not typically buy options, so the put/call ratio indicator more closely tracks the sentiment of actively-managed funds.

MX:MRK / Merck & Co., Inc. Historical Put/Call Ratio
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)
2026-05-01 2026-03-31 13F MERCK COM 58933Y105 57,421 -9,661 -14.40 6,956 -2.29 0.6103
2026-02-05 2025-12-31 13F MERCK COM 58933Y105 67,082 4,504 7.20 7,118 35.53 0.6339
2025-10-30 2025-09-30 13F MERCK COM 58933Y105 62,578 -4,032 -6.05 5,252 -0.38 0.5659
2025-08-07 2025-06-30 13F MERCK COM 58933Y105 66,610 -5,026 -7.02 5,273 -18.01 0.6155
2025-05-13 2025-03-31 13F MERCK COM 58933Y105 71,636 -668 -0.92 6,430 -10.60 0.7916
2025-02-13 2024-12-31 13F MERCK COM 58933Y105 72,304 -594 -0.81 7,193 -13.12 0.8892
2024-11-05 2024-09-30 13F MERCK COM 58933Y105 72,898 430 0.59 8,278 -7.72 1.0228
2024-08-12 2024-06-30 13F MERCK COM 58933Y105 72,468 -779 -1.06 8,972 -7.17 1.1782
2024-05-13 2024-03-31 13F MERCK COM 58933Y105 73,247 -220 -0.30 9,665 20.66 1.2645
2024-02-07 2023-12-31 13F MERCK COM 58933Y105 73,467 -152 -0.21 8,009 5.67 1.1316
2023-11-13 2023-09-30 13F MERCK COM 58933Y105 73,619 36 0.05 7,579 -10.73 1.1481
2023-08-14 2023-06-30 13F MERCK COM 58933Y105 73,583 2,492 3.51 8,491 12.26 1.2631
2023-05-02 2023-03-31 13F MERCK COM 58933Y105 71,091 -278 -0.39 7,563 -4.48 1.1815
2023-02-14 2022-12-31 13F MERCK COM 58933Y105 71,369 -373 -0.52 7,918 131,866.67 1.2677
2022-11-08 2022-09-30 13F MERCK COM 58933Y105 71,742 2,068 2.97 6 0.00 1.1056
2022-08-11 2022-06-30 13F MERCK COM 58933Y105 69,674 1,971 2.91 6 20.00 1.0997
2022-05-09 2022-03-31 13F MERCK COM 58933Y105 67,703 -2,166 -3.10 6 0.00 0.8649
2022-02-07 2021-12-31 13F MERCK COM 58933Y105 69,869 16,778 31.60 5 66.67 0.8362
2021-11-08 2021-09-30 13F MERCK COM 58933Y105 53,091 535 1.02 4 -25.00 0.6828
2021-08-13 2021-06-30 13F MERCK COM 58933Y105 52,556 -13 -0.02 4 0.00 0.6994
2021-05-10 2021-03-31 13F MERCK & CO. COM 58933Y105 52,569 -9,222 -14.92 4 -20.00 0.7597
2021-02-10 2020-12-31 13F MERCK & CO. COM 58933Y105 61,791 2,772 4.70 5 25.00 1.0248
2020-11-10 2020-09-30 13F MERCK & CO. COM 58933Y105 59,019 10,660 22.04 5 -99.89 1.1506
2020-08-05 2020-06-30 13F MERCK & CO. COM 58933Y105 48,359 4,025 9.08 3,740 9.65 1.0329
2020-05-07 2020-03-31 13F MERCK & CO. COM 58933Y105 44,334 12,625 39.82 3,411 18.27 1.1793
2020-02-10 2019-12-31 13F MERCK COM 58933Y105 31,709 12,729 67.07 2,884 80.48 0.8897
2019-11-05 2019-09-30 13F MERCK COM 58933Y105 18,980 6,850 56.47 1,598 57.13 0.5374
2019-08-05 2019-06-30 13F MERCK COM 58933Y105 12,130 2,290 23.27 1,017 24.33 0.3593
2019-04-30 2019-03-31 13F MERCK COM 58933Y105 9,840 -44 -0.45 818 8.34 0.3012
2019-01-22 2018-12-31 13F MERCK COM 58933Y105 9,884 0 0.00 755 7.70 0.3200
2018-10-26 2018-09-30 13F MERCK COM 58933Y105 9,884 9,884 701 0.2803
2018-05-04 2018-03-31 13F MERCK & CO INC NEW COM COM 58933Y105 0 -8,020 -100.00 0 -100.00
2018-03-15 2017-12-31 13F MERCK & CO INC NEW COM COM 58933Y105 8,020 8,020 451 0.4547
Disclosed Put Options
File
Date
Effective
Date
Form Security Class ID Opt Avg Share Price Shares ΔShares
(%)
Value
(x1000)
ΔValue
(%)
Prior Allocation
(%)
Allocation
(%)
ΔAllocation
(%)
Cost Basis
(x1000)
Profit
(x1000)
Return
(%)
2026-05-01 2026-03-31 13F MERCK COM Put 0 -100.00 0 -100.00 n/a n/a n/a
2026-02-05 2025-12-31 13F MERCK COM Put 1,000 105 n/a n/a n/a
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.