NewMarket Corporation
US ˙ NYSE ˙ US6515871076

SecurityNEU / NewMarket Corporation
InstitutionSei Investments Co
Latest Disclosed Ownership5,124 shares
Latest Disclosed Value $ 3,521,271
Sei Investments Co ownership in NEU / NewMarket Corporation

On February 13, 2026 - Sei Investments Co filed a 13F-HR form disclosing ownership of 5,124 shares of NewMarket Corporation (US:NEU) valued at $3,521,520 USD as of December 31, 2025. The entity filed a previous 13F-HR on November 13, 2025 disclosing 7,494 shares of NewMarket Corporation. This represents a change in shares of -31.63% during the quarter. The current value of the position is $4,004,304 USD.

Sei Investments Co has a history of taking positions in derivatives of the underlying security (NEU) 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.

NEU / NewMarket Corporation 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)
2026-02-13 2025-12-31 13F NEWMARKET COM 651587107 5,124 -2,370 -31.63 3,521 -43.27 0.0035
2025-11-13 2025-09-30 13F NEWMARKET COM 651587107 7,494 -1,922 -20.41 6,207 -4.55 0.0067
2025-08-14 2025-06-30 13F NEWMARKET COM 651587107 9,416 3,297 53.88 6,504 87.62 0.0075
2025-05-14 2025-03-31 13F/A-1 NEWMARKET COM 651587107 6,119 72 1.19 3,466 8.48 0.0045
2025-05-13 2025-03-31 13F NEWMARKET COM 651587107 6,110 63 3,282 0.0036
2025-02-11 2024-12-31 13F NEWMARKET COM 651587107 6,047 -5,006 -45.29 3,195 -47.61 0.0041
2024-11-12 2024-09-30 13F NEWMARKET COM 651587107 11,053 2,636 31.32 6,100 40.56 0.0079
2024-08-13 2024-06-30 13F NEWMARKET COM 651587107 8,417 -907 -9.73 4,340 -26.66 0.0061
2024-05-07 2024-03-31 13F NEWMARKET COM 651587107 9,324 -433 -4.44 5,916 11.10 0.0087
2024-02-14 2023-12-31 13F NEWMARKET COM 651587107 9,757 -618 -5.96 5,326 12.77 0.0085
2023-11-14 2023-09-30 13F NEWMARKET COM 651587107 10,375 262 2.59 4,723 16.13 0.0085
2023-08-11 2023-06-30 13F NEWMARKET COM 651587107 10,113 -76 -0.75 4,066 9.39 0.0071
2023-05-12 2023-03-31 13F NEWMARKET COM 651587107 10,189 5,234 105.63 3,717 141.36 0.0069
2023-02-10 2022-12-31 13F NEWMARKET COM 651587107 4,955 -3,466 -41.16 1,540 -39.18 0.0034
2022-11-14 2022-09-30 13F NEWMARKET COM 651587107 8,421 -492 -5.52 2,532 -7.73 0.0056
2022-08-15 2022-06-30 13F NEWMARKET COM 651587107 8,913 2,184 32.46 2,744 24.22 0.0059
2022-05-13 2022-03-31 13F NEWMARKET COM 651587107 6,729 -729 -9.77 2,209 -12.10 0.0044
2022-02-14 2021-12-31 13F NEWMARKET COM 651587107 7,458 3,073 70.08 2,513 76.23 0.0047
2021-11-12 2021-09-30 13F NEWMARKET COM 651587107 4,385 -806 -15.53 1,426 -13.10 0.0030
2021-08-06 2021-06-30 13F NEWMARKET COM 651587107 5,191 -550 -9.58 1,641 -23.67 0.0036
2021-05-12 2021-03-31 13F NEWMARKET COM 651587107 5,741 -163 -2.76 2,150 -6.81 0.0054
2021-02-08 2020-12-31 13F NEWMARKET COM 651587107 5,904 -3,558 -37.60 2,307 -27.84 0.0060
2020-12-04 2020-09-30 13F/A-1 NEWMARKET COM 651587107 9,462 -7,173 -43.12 3,197 -51.30 0.0093
2020-11-06 2020-09-30 13F NEWMARKET COM 651587107 9,732 -6,903 3,289 7,919.1807
2020-08-17 2020-06-30 13F/A-1 NEWMARKET COM 651587107 16,635 2,471 17.45 6,565 21.13 0.0204
2020-08-11 2020-06-30 13F NEWMARKET COM 651587107 16,158 1,994 7,421 20,129.8575
2020-05-14 2020-03-31 13F NEWMARKET COM 651587107 14,164 -518 -3.53 5,420 -23.26 0.0199
2020-02-06 2019-12-31 13F NEWMARKET COM 651587107 14,682 5,365 57.58 7,063 62.82 0.0211
2019-11-12 2019-09-30 13F NEWMARKET COM 651587107 9,317 8,029 623.37 4,338 742.33 0.0111
2019-08-14 2019-06-30 13F NEWMARKET COM 651587107 1,288 -901 -41.16 515 -45.62 0.0017
2019-05-15 2019-03-31 13F NEWMARKET COM 651587107 2,189 -722 -24.80 947 -19.68 0.0032
2019-02-13 2018-12-31 13F NEWMARKET COM 651587107 2,911 2 0.07 1,179 0.00 0.0042
2018-11-08 2018-09-30 13F NEWMARKET COM 651587107 2,909 -974 -25.08 1,179 -24.90 0.0043
2018-08-03 2018-06-30 13F NEWMARKET COM 651587107 3,883 -9 -0.23 1,570 0.38 0.0053
2018-05-11 2018-03-31 13F NEWMARKET COM 651587107 3,892 117 3.10 1,564 4.34 0.0060
2018-02-08 2017-12-31 13F NEWMARKET COM 651587107 3,775 -115 -2.96 1,499 -9.48 0.0052
2017-11-06 2017-09-30 13F NEWMARKET COM 651587107 3,890 124 3.29 1,656 -4.50 0.0059
2017-07-31 2017-06-30 13F NEWMARKET COM 651587107 3,766 267 7.63 1,734 9.40 0.0069
2017-05-05 2017-03-31 13F NEWMARKET COM 651587107 3,499 3,058 693.42 1,585 752.15 0.0069
2017-02-02 2016-12-31 13F NEWMARKET COM 651587107 441 -1,190 -72.96 186 -73.43 0.0009
2016-11-04 2016-09-30 13F NEWMARKET COM 651587107 1,631 355 27.82 700 32.33 0.0036
2016-08-11 2016-06-30 13F NEWMARKET COM 651587107 1,276 169 15.27 529 20.78 0.0032
2016-05-10 2016-03-31 13F/A-1 NEWMARKET COM 651587107 1,107 54 5.13 438 9.23 0.0027
2016-02-03 2015-12-31 13F NEWMARKET COM 651587107 1,053 461 77.87 401 89.15 0.0024
2015-11-02 2015-09-30 13F/A-1 NEWMARKET COM 651587107 592 5 0.85 212 -18.77 0.0019
2015-10-30 2015-09-30 13F NEWMARKET COM 651587107 592 212
2015-08-07 2015-06-30 13F/A-1 NEWCASTLE INVT CORP PUT 651587107 0 -383 -100.00 0 -100.00
2015-08-07 2015-06-30 13F/A-1 NEWMARKET COM 651587107 587 204 53.26 261 45.00 0.0024
2015-08-04 2015-06-30 13F NEWMARKET COM 651587107 587 204 261 0.0024
2015-05-14 2015-03-31 13F/A-1 NEWMARKET COM 651587107 383 285 290.82 180 350.00 0.0016
2015-05-01 2015-03-31 13F NEWCASTLE INVT CORP PUT 651587107 383 383 180 0.0016
2015-02-10 2014-12-31 13F NEWMARKET COM 651587107 98 98 40 0.0004
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
(%)
2015-08-07 2015-06-30 13F/A NEWCASTLE INVT CORP PUT 0 -100.00 0 -100.00 n/a n/a n/a
2015-05-01 2015-03-31 13F NEWCASTLE INVT CORP PUT 383 180 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.