Westlake Corporation
US ˙ NYSE ˙ US9604131022

SecurityWLK / Westlake Corporation
InstitutionCitigroup Inc
Latest Disclosed Ownership54,559 shares
Latest Disclosed Value $ 6,373,582
Citigroup Inc ownership in WLK / Westlake Corporation

On May 11, 2026 - Citigroup Inc filed a 13F-HR form disclosing ownership of 54,559 shares of Westlake Corporation (US:WLK) valued at $6,373,582 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 13, 2026 disclosing 27,337 shares of Westlake Corporation. This represents a change in shares of 99.58% during the quarter. The current value of the position is $4,713,352 USD.

Citigroup Inc has a history of taking positions in derivatives of the underlying security (WLK) in the form of stock options. The firm currently holds call options representing 0 of underlying shares valued at $0 USD and put options representing 0 of underlying shares valued at $0 USD .

Note: prior versions of this page mistakenly stated that the share values represented the number of options, not the number of underlying shares. For more information on the data backing these reports, please see the SEC document Frequently Asked Questions About Form 13F.

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.

Upgrade to unlock premium data and export to Excel .

Institutional Put/Call Ratios
(Premium Subscription Required)

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.

WLK / Westlake 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)
2026-05-11 2026-03-31 13F WESTLAKE COM 960413102 54,559 27,222 99.58 6,374 215.34 0.0014
2026-02-13 2025-12-31 13F WESTLAKE COM 960413102 27,337 -89,814 -76.67 2,021 -77.61 0.0009
2025-11-10 2025-09-30 13F WESTLAKE COM 960413102 117,151 44,525 61.31 9,028 63.71 0.0040
2025-08-11 2025-06-30 13F WESTLAKE COM 960413102 72,626 44,374 157.06 5,514 95.12 0.0027
2025-05-12 2025-03-31 13F WESTLAKE COM 960413102 28,252 -4,885 -14.74 2,826 -25.61 0.0014
2025-02-12 2024-12-31 13F WESTLAKE COM 960413102 33,137 23,247 235.06 3,799 155.65 0.0023
2024-11-12 2024-09-30 13F WESTLAKE COM 960413102 9,890 2,194 28.51 1,486 33.39 0.0009
2024-08-12 2024-06-30 13F WESTLAKE COM 960413102 7,696 -809 -9.51 1,115 -14.24 0.0007
2024-05-10 2024-03-31 13F WESTLAKE COM 960413102 8,505 -18,806 -68.86 1,300 -66.01 0.0009
2024-02-09 2023-12-31 13F WESTLAKE COM 960413102 27,311 -22,228 -44.87 3,822 -38.12 0.0027
2023-12-06 2023-09-30 13F/A-1 WESTLAKE COM 960413102 49,539 3,636 7.92 6,176 12.62 0.0046
2023-11-09 2023-09-30 13F WESTLAKE COM 960413102 49,539 3,636 6,176 0.0018
2023-08-10 2023-06-30 13F WESTLAKE COM 960413102 45,903 24,217 111.67 5,484 118.05 0.0036
2023-05-11 2023-03-31 13F WESTLAKE COM 960413102 21,686 -2,035 -8.58 2,515 3.41 0.0018
2023-02-09 2022-12-31 13F WESTLAKE COM 960413102 23,721 -35,316 -59.82 2,432 -52.59 0.0019
2022-11-10 2022-09-30 13F WESTLAKE COM 960413102 59,037 -2,891 -4.67 5,130 -15.49 0.0037
2022-08-10 2022-06-30 13F WESTLAKE COM 960413102 61,928 2,280 3.82 6,070 -17.54 0.0045
2022-05-12 2022-03-31 13F WESTLAKE COM 960413102 59,648 -4,162 -6.52 7,361 18.74 0.0045
2022-02-10 2021-12-31 13F WESTLAKE CHEM COM 960413102 63,810 -3,703 -5.48 6,199 0.75 0.0033
2021-11-10 2021-09-30 13F WESTLAKE CHEM COM 960413102 67,513 29,556 77.87 6,153 79.96 0.0036
2021-08-10 2021-06-30 13F WESTLAKE CHEM COM 960413102 37,957 -11,764 -23.66 3,419 -22.56 0.0021
2021-05-13 2021-03-31 13F WESTLAKE CHEM COM 960413102 49,721 44,484 849.42 4,415 933.96 0.0029
2021-02-11 2020-12-31 13F WESTLAKE CHEM COM 960413102 5,237 631 13.70 427 46.74 0.0003
2020-11-12 2020-09-30 13F WESTLAKE CHEM COM 960413102 4,606 -9,537 -67.43 291 -61.66 0.0002
2020-08-12 2020-06-30 13F WESTLAKE CHEM COM 960413102 14,143 -26,991 -65.62 759 -51.66 0.0006
2020-05-12 2020-03-31 13F WESTLAKE CHEM COM 960413102 41,134 -1,386 -3.26 1,570 -47.37 0.0014
2020-02-12 2019-12-31 13F WESTLAKE CHEM COM 960413102 42,520 -32,253 -43.13 2,983 -39.10 0.0022
2019-11-08 2019-09-30 13F WESTLAKE CHEM COM 960413102 74,773 23,527 45.91 4,898 37.62 0.0039
2019-08-12 2019-06-30 13F WESTLAKE CHEM COM 960413102 51,246 -86,465 -62.79 3,559 -61.92 0.0029
2019-05-13 2019-03-31 13F WESTLAKE CHEM COM 960413102 137,711 -149,901 -52.12 9,346 -50.89 0.0090
2019-02-12 2018-12-31 13F WESTLAKE CHEM COM 960413102 287,612 213,441 287.77 19,032 208.76 0.0193
2018-11-13 2018-09-30 13F WESTLAKE CHEM COM 960413102 74,171 9,811 15.24 6,164 -11.01 0.0055
2018-08-10 2018-06-30 13F WESTLAKE CHEM COM 960413102 64,360 -120,320 -65.15 6,927 -66.25 0.0064
2018-05-11 2018-03-31 13F WESTLAKE CHEM COM 960413102 184,680 -359,872 -66.09 20,527 -64.61 0.0169
2018-02-12 2017-12-31 13F WESTLAKE CHEM COM 960413102 544,552 -600,535 -52.44 58,010 -39.03 0.0465
2017-11-13 2017-09-30 13F WESTLAKE CHEM COM 960413102 1,145,087 11,027 0.97 95,145 26.71 0.0779
2017-08-11 2017-06-30 13F WESTLAKE CHEM COM 960413102 1,134,060 573,604 102.35 75,086 102.83 0.0677
2017-05-12 2017-03-31 13F WESTLAKE CHEM COM 960413102 560,456 403,207 256.41 37,019 320.48 0.0330
2017-02-10 2016-12-31 13F WESTLAKE CHEM COM 960413102 157,249 -58,770 -27.21 8,804 -23.83 0.0079
2016-11-10 2016-09-30 13F WESTLAKE CHEM COM 960413102 216,019 -49,617 -18.68 11,558 1.38 0.0108
2016-08-12 2016-06-30 13F WESTLAKE CHEM COM 960413102 265,636 23,989 9.93 11,401 1.90 0.0116
2016-05-13 2016-03-31 13F WESTLAKE CHEM COM 960413102 241,647 -214,112 -46.98 11,188 -54.81 0.0126
2016-02-12 2015-12-31 13F WESTLAKE CHEM COM 960413102 455,759 60,176 15.21 24,756 20.61 0.0247
2015-11-13 2015-09-30 13F WESTLAKE CHEM COM 960413102 395,583 387,503 4,795.83 20,526 3,605.05 0.0192
2015-08-13 2015-06-30 13F WESTLAKE CHEM COM 960413102 8,080 4,456 122.96 554 112.26 0.0005
2015-05-14 2015-03-31 13F WESTLAKE CHEM COM 960413102 3,624 573 18.78 261 40.32 0.0003
2015-02-17 2014-12-31 13F WESTLAKE CHEM COM 960413102 3,051 -4,005 -56.76 186 -69.56 0.0002
2014-11-14 2014-09-30 13F WESTLAKE CHEM COM 960413102 7,056 3,679 108.94 611 115.14 0.0005
2014-08-14 2014-06-30 13F WESTLAKE CHEM COM 960413102 3,377 -1,623 -32.46 284 -14.20 0.0003
2014-05-15 2014-03-31 13F WESTLAKE CHEM COM 960413102 5,000 3,292 192.74 331 59.13 0.0003
2014-02-14 2013-12-31 13F WESTLAKE CHEM COM 960413102 1,708 -242 -12.41 208 1.96 0.0002
2013-11-14 2013-09-30 13F WESTLAKE CHEM COM 960413102 1,950 1,731 790.41 204 871.43 0.0002
2013-08-14 2013-06-30 13F WESTLAKE CHEM COM 960413102 219 219 21 0.0000
Disclosed Call 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
(%)
2021-02-11 2020-12-31 13F WESTLAKE CHEM COM Call 0 -100.00 0 -100.00 n/a n/a n/a
2020-11-12 2020-09-30 13F WESTLAKE CHEM COM Call 1,100 -35.29 70 -23.08 n/a n/a n/a
2020-08-12 2020-06-30 13F WESTLAKE CHEM COM Call 1,700 6.25 91 49.18 n/a n/a n/a
2020-05-12 2020-03-31 13F WESTLAKE CHEM COM Call 1,600 700.00 61 335.71 n/a n/a n/a
2020-02-12 2019-12-31 13F WESTLAKE CHEM COM Call 200 -96.49 14 -96.25 n/a n/a n/a
2019-11-08 2019-09-30 13F WESTLAKE CHEM COM Call 5,700 -53.66 373 -56.32 n/a n/a n/a
2019-08-12 2019-06-30 13F WESTLAKE CHEM COM Call 12,300 161.70 854 167.71 n/a n/a n/a
2019-05-13 2019-03-31 13F WESTLAKE CHEM COM Call 4,700 370.00 319 383.33 n/a n/a n/a
2019-02-12 2018-12-31 13F WESTLAKE CHEM COM Call 1,000 -68.75 66 -75.19 n/a n/a n/a
2018-11-13 2018-09-30 13F WESTLAKE CHEM COM Call 3,200 -13.51 266 -33.17 n/a n/a n/a
2018-08-10 2018-06-30 13F WESTLAKE CHEM COM Call 3,700 -58.43 398 -59.76 n/a n/a n/a
2018-05-11 2018-03-31 13F WESTLAKE CHEM COM Call 8,900 30.88 989 36.60 n/a n/a n/a
2018-02-12 2017-12-31 13F WESTLAKE CHEM COM Call 6,800 70.00 724 118.07 n/a n/a n/a
2017-11-13 2017-09-30 13F WESTLAKE CHEM COM Call 4,000 300.00 332 403.03 n/a n/a n/a
2017-08-11 2017-06-30 13F WESTLAKE CHEM COM Call 1,000 11.11 66 11.86 n/a n/a n/a
2017-05-12 2017-03-31 13F WESTLAKE CHEM COM Call 900 -25.00 59 -11.94 n/a n/a n/a
2017-02-10 2016-12-31 13F WESTLAKE CHEM COM Call 1,200 9.09 67 13.56 n/a n/a n/a
2016-11-10 2016-09-30 13F WESTLAKE CHEM COM Call 1,100 1,000.00 59 1,375.00 n/a n/a n/a
2016-08-12 2016-06-30 13F WESTLAKE CHEM COM Call 100 -92.86 4 -93.85 n/a n/a n/a
2016-05-13 2016-03-31 13F WESTLAKE CHEM COM Call 1,400 -26.32 65 -36.89 n/a n/a n/a
2016-02-12 2015-12-31 13F WESTLAKE CHEM COM Call 1,900 -70.31 103 -68.98 n/a n/a n/a
2015-11-13 2015-09-30 13F WESTLAKE CHEM COM Call 6,400 -5.88 332 -28.76 n/a n/a n/a
2015-08-13 2015-06-30 13F WESTLAKE CHEM COM Call 6,800 466 n/a n/a n/a
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
(%)
2021-05-13 2021-03-31 13F WESTLAKE CHEM COM Put 0 -100.00 0 -100.00 n/a n/a n/a
2021-02-11 2020-12-31 13F WESTLAKE CHEM COM Put 1,000 -50.00 82 -34.92 n/a n/a n/a
2020-11-12 2020-09-30 13F WESTLAKE CHEM COM Put 2,000 -4.76 126 11.50 n/a n/a n/a
2020-08-12 2020-06-30 13F WESTLAKE CHEM COM Put 2,100 -55.32 113 -36.87 n/a n/a n/a
2020-05-12 2020-03-31 13F WESTLAKE CHEM COM Put 4,700 20.51 179 -34.67 n/a n/a n/a
2020-02-12 2019-12-31 13F WESTLAKE CHEM COM Put 3,900 -45.07 274 -41.08 n/a n/a n/a
2019-11-08 2019-09-30 13F WESTLAKE CHEM COM Put 7,100 108.82 465 97.03 n/a n/a n/a
2019-08-12 2019-06-30 13F WESTLAKE CHEM COM Put 3,400 36.00 236 38.82 n/a n/a n/a
2019-05-13 2019-03-31 13F WESTLAKE CHEM COM Put 2,500 56.25 170 60.38 n/a n/a n/a
2019-02-12 2018-12-31 13F WESTLAKE CHEM COM Put 1,600 -65.96 106 -72.89 n/a n/a n/a
2018-11-13 2018-09-30 13F WESTLAKE CHEM COM Put 4,700 -4.08 391 -25.81 n/a n/a n/a
2018-08-10 2018-06-30 13F WESTLAKE CHEM COM Put 4,900 157.89 527 149.76 n/a n/a n/a
2018-05-11 2018-03-31 13F WESTLAKE CHEM COM Put 1,900 375.00 211 390.70 n/a n/a n/a
2018-02-12 2017-12-31 13F WESTLAKE CHEM COM Put 400 -80.95 43 -75.29 n/a n/a n/a
2017-11-13 2017-09-30 13F WESTLAKE CHEM COM Put 2,100 0.00 174 25.18 n/a n/a n/a
2017-08-11 2017-06-30 13F WESTLAKE CHEM COM Put 2,100 -82.79 139 -82.75 n/a n/a n/a
2017-05-12 2017-03-31 13F WESTLAKE CHEM COM Put 12,200 806 n/a n/a n/a
2017-02-10 2016-12-31 13F WESTLAKE CHEM COM Put 0 -100.00 0 -100.00 n/a n/a n/a
2016-11-10 2016-09-30 13F WESTLAKE CHEM COM Put 7,500 200.00 401 274.77 n/a n/a n/a
2016-08-12 2016-06-30 13F WESTLAKE CHEM COM Put 2,500 257.14 107 234.38 n/a n/a n/a
2016-05-13 2016-03-31 13F WESTLAKE CHEM COM Put 700 -50.00 32 -57.89 n/a n/a n/a
2016-02-12 2015-12-31 13F WESTLAKE CHEM COM Put 1,400 -88.14 76 -87.58 n/a n/a n/a
2015-11-13 2015-09-30 13F WESTLAKE CHEM COM Put 11,800 90.32 612 44.00 n/a n/a n/a
2015-08-13 2015-06-30 13F WESTLAKE CHEM COM Put 6,200 425 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.