WESTLAKE CORPORATION WLK
COM · Common Stock · CUSIP 960413102 · ISIN US9604131022
American petrochemical company
- SectorMaterials
- IndustryIndustrial Organic Chemicals
- HeadquartersHouston, TX
- Founded1986
- Websitewestlake.com
- FilingsSEC EDGAR
* Summed across managers. Shares that two managers' reports both contain – a subsidiary's holdings that its parent's report includes too, or a sub-adviser's in its client's – are counted once ($24.6m this quarter). Holder counts are more reliable. Shares outstanding: 128.1m as of 2026-04-29, from the company's own SEC filing; the percentage can still exceed 100%: lent-out shares are counted by the lender and the buyer, and some reports overlap without saying so. Implied quarter-end price ≈ $116.73. Options: 9 managers hold calls ($26.7m notional), 10 hold puts ($16.9m).
Trends to Q1 2026
Institutional holders
Managers reporting a position, each quarter
Numbers
| Quarter | Holders |
|---|---|
| Q3 2022 | 321 |
| Q4 2022 | 343 |
| Q1 2023 | 342 |
| Q2 2023 | 340 |
| Q3 2023 | 335 |
| Q4 2023 | 357 |
| Q1 2024 | 347 |
| Q2 2024 | 382 |
| Q3 2024 | 403 |
| Q4 2024 | 378 |
| Q1 2025 | 362 |
| Q2 2025 | 308 |
| Q3 2025 | 305 |
| Q4 2025 | 298 |
| Q1 2026 | 339 |
Buyers vs sellers
Managers adding to or starting a position, vs cutting or selling out
Numbers
| Quarter | Bought or added | Cut or sold out |
|---|---|---|
| Q2 2024 | 187 | 164 |
| Q3 2024 | 210 | 170 |
| Q4 2024 | 174 | 195 |
| Q1 2025 | 183 | 175 |
| Q2 2025 | 168 | 200 |
| Q3 2025 | 158 | 160 |
| Q4 2025 | 143 | 176 |
| Q1 2026 | 203 | 132 |
Calls vs puts
Options held, notional value, last 4 quarters. P/C = puts ÷ calls
Numbers
| Quarter | Calls | Puts | P/C |
|---|---|---|---|
| Q2 2025 | $19.5m | $58.1m | 2.98 |
| Q3 2025 | $19.3m | $57.8m | 2.99 |
| Q4 2025 | $18.4m | $51.2m | 2.78 |
| Q1 2026 | $26.7m | $16.9m | 0.63 |
Biggest buyers
| Capital World Investors | Added | +2.0m |
| FMR LLC | Added | +1.1m |
| Orbis Allan Gray Ltd | Added | +906.9k |
| GOLDMAN SACHS GROUP INC | Added | +639.4k |
| CITADEL ADVISORS LLC | Added | +512.3k |
| SCHRODER INVESTMENT MANAGEMENT GROUP | New | +374.5k |
| Balyasny Asset Management L.P. | New | +369.7k |
| AQR CAPITAL MANAGEMENT LLC | Added | +239.5k |
| PRICE T ROWE ASSOCIATES INC /MD/ | Added | +198.7k |
| BRANDES INVESTMENT PARTNERS, LP | Added | +172.3k |
Biggest sellers
| WELLINGTON MANAGEMENT GROUP LLP | Reduced | -2.4m |
| VICTORY CAPITAL MANAGEMENT INC | Reduced | -1.1m |
| THOMPSON SIEGEL & WALMSLEY LLC | Reduced | -533.3k |
| Holocene Advisors, LP | Reduced | -490.6k |
| DIMENSIONAL FUND ADVISORS LP | Reduced | -419.7k |
| ANTIPODES PARTNERS Ltd | Sold out | -416.5k |
| VOLORIDGE INVESTMENT MANAGEMENT, LLC | Sold out | -349.0k |
| MILLENNIUM MANAGEMENT LLC | Reduced | -342.8k |
| JACOBS LEVY EQUITY MANAGEMENT, INC | Reduced | -319.4k |
| Woodline Partners LP | Reduced | -291.1k |
Biggest calls
| SUSQUEHANNA INTERNATIONAL GROUP, LLP | Added | $10.2m87.0k shares |
| CITADEL ADVISORS LLC | Added | $8.1m69.1k shares |
| Twin Tree Management, LP | Reduced | $2.0m16.8k shares |
| Walleye Capital LLC | Reduced | $2.0m16.8k shares |
| JANE STREET GROUP, LLC | Reduced | $1.6m13.7k shares |
| CenterStar Asset Management, LLC | New | $852.8k7.3k shares |
| Walleye Trading LLC | Reduced | $712.6k6.1k shares |
| SIMPLEX TRADING, LLC | Added | $712.6k6.1k shares |
| GROUP ONE TRADING LLC | Added | $665.9k5.7k shares |
Biggest puts
| CITADEL ADVISORS LLC | Reduced | $7.3m62.5k shares |
| SUSQUEHANNA INTERNATIONAL GROUP, LLP | Reduced | $3.0m26.0k shares |
| JANE STREET GROUP, LLC | Reduced | $1.7m14.6k shares |
| Polymer Capital Management (US) LLC | New | $1.2m10.0k shares |
| Twin Tree Management, LP | Added | $969.6k8.3k shares |
| Walleye Trading LLC | Reduced | $922.9k7.9k shares |
| D. E. Shaw & Co., Inc. | Unchanged | $771.0k6.6k shares |
| SIMPLEX TRADING, LLC | Added | $607.5k5.2k shares |
| Walleye Capital LLC | Reduced | $280.4k2.4k shares |
| GROUP ONE TRADING LLC | Added | $163.5k1.4k shares |
Options at notional value: the value of the shares the contracts control, as filers report them, not what the options cost. Not included in the holders, shares or buying above.
Insider purchases and sales in Q1 2026
Shares bought or sold by the company's own officers, directors and 10% owners, in the open market or privately, as they reported to the SEC on Form 4 (due within two business days of the trade). Grants, option exercises, shares withheld for tax and gifts aren't included.
Officers and directors buying vs selling
Number of people, by quarter (10% owners not included)
Numbers
| Quarter | Buying | Bought | Selling | Sold | Sold under a plan |
|---|---|---|---|---|---|
| Q2 2024 | 0 | — | 2 | $1.3m | — |
| Q3 2024 | 0 | — | 0 | — | — |
| Q4 2024 | 0 | — | 1 | $453.4k | — |
| Q1 2025 | 0 | — | 0 | — | — |
| Q2 2025 | 1 | $7.8k | 1 | $6.0k | — |
| Q3 2025 | 0 | — | 0 | — | — |
| Q4 2025 | 0 | — | 1 | $3.0m | — |
| Q1 2026 | 0 | — | 2 | $4.1m | — |
| Date | Insider | Trade | Value |
|---|---|---|---|
| 2026-03-27 | Bender Mark Steven EVP & CFO | Sold | $1.8m16.4k shares |
| 2026-03-27 | Buesinger Robert F. EVP, PEM Segment Head | Sold | $461.0k4.0k shares |
| 2026-02-27 | Bender Mark Steven EVP & CFO | Sold | $1.8m17.4k shares |
Their holding: how much the trade added to or took from the insider's holding (direct, or the trust or fund named). The same trade is sometimes reported by more than one insider, such as a fund and the director who represents it; totals count it once. A value is left blank where the reported price is far from the market price (usually a typo).
Holders, Q1 2026
| Manager | Shares | Change |
|---|---|---|
| Orbis Allan Gray Ltd 2.61% of their portfolio | 5.3m $618.4m | Added +906.9k |
| Capital World Investors 0.07% of their portfolio | 4.2m $491.9m | Added +2.0m |
| BlackRock, Inc. 0.01% of their portfolio | 3.1m $359.7m | Reduced -182.3k |
| PRICE T ROWE ASSOCIATES INC /MD/ 0.03% of their portfolio | 2.4m $281.2m | Added +198.7k |
| BRANDES INVESTMENT PARTNERS, LP 1.52% of their portfolio | 1.8m $215.3m | Added +172.3k |
| WELLINGTON MANAGEMENT GROUP LLP 0.04% of their portfolio | 1.8m $209.5m | Reduced -2.4m |
| VANGUARD PORTFOLIO MANAGEMENT LLC 0.01% of their portfolio | 1.8m $206.7m | First filing |
| DIMENSIONAL FUND ADVISORS LP 0.04% of their portfolio | 1.5m $171.3m | Reduced -419.7k |
| VANGUARD CAPITAL MANAGEMENT LLC 0.00% of their portfolio | 1.5m $170.0m | First filing |
| GOLDMAN SACHS GROUP INC 0.02% of their portfolio | 1.4m $162.8m | Added +639.4k |
| STATE STREET CORP 0.01% of their portfolio | 1.4m $161.3m | Reduced -16.1k |
| FMR LLC 0.01% of their portfolio | 1.3m $153.3m | Added +1.1m |
| UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC 0.02% of their portfolio | 981.4k $114.6m | Added +56.7k |
| MIRAE ASSET GLOBAL ETFS HOLDINGS Ltd. 0.15% of their portfolio | 944.0k $110.3m | Added +67.1k |
| UBS Group AG 0.02% of their portfolio | 811.3k $94.8m | Added +163.3k |
| Holocene Advisors, LP 0.21% of their portfolio | 730.0k $85.3m | Reduced -490.6k |
| CITADEL ADVISORS LLC 0.06% of their portfolio | 715.6k $83.6m | Added +512.3k |
| GEODE CAPITAL MANAGEMENT, LLC 0.00% of their portfolio | 614.3k $71.8m | Added +19.4k |
| Nuveen, LLC 0.02% of their portfolio | 564.7k $66.0m | Reduced -88.2k |
| MORGAN STANLEY 0.00% of their portfolio | 486.5k $56.8m | Reduced -273.1k |
| Erste Asset Management GmbH 0.42% of their portfolio | 395.0k $45.8m | Reduced -25.0k |
| SCHRODER INVESTMENT MANAGEMENT GROUP 0.04% of their portfolio | 374.5k $43.4m | New |
| Balyasny Asset Management L.P. 0.08% of their portfolio | 369.7k $43.2m | New |
| JACOBS LEVY EQUITY MANAGEMENT, INC 0.17% of their portfolio | 349.0k $40.8m | Reduced -319.4k |
| Woodline Partners LP 0.15% of their portfolio | 337.1k $39.4m | Reduced -291.1k |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC 0.01% of their portfolio | 311.8k $36.4m | Added +14.5k |
| NEW YORK STATE COMMON RETIREMENT FUND 0.05% of their portfolio | 309.6k $36.2m | Unchanged |
| ProShare Advisors LLC 0.05% of their portfolio | 295.8k $34.6m | Reduced -139.4k |
| Allspring Global Investments Holdings, LLC 0.06% of their portfolio | 285.4k $33.3m | Reduced -221.3k |
| JANUS HENDERSON GROUP PLC 0.02% of their portfolio | 269.8k $31.5m | Reduced -64.8k |
| NORTHERN TRUST CORP 0.00% of their portfolio | 269.1k $31.4m | Added +515 |
| FEDERATED HERMES, INC. 0.05% of their portfolio | 266.7k $31.2m | Added +158.9k |
| AQR CAPITAL MANAGEMENT LLC 0.01% of their portfolio | 260.1k $30.4m | Added +239.5k |
| VAN LANSCHOT KEMPEN INVESTMENT MANAGEMENT N.V. 0.25% of their portfolio | 244.3k $28.5m | Added +8.4k |
| BANK OF AMERICA CORP /DE/ 0.00% of their portfolio | 237.0k $27.7m | Added +52.6k |
| D. E. Shaw & Co., Inc. 0.02% of their portfolio | 233.2k $27.2m | Reduced -253.1k |
| Merewether Investment Management, LP 0.50% of their portfolio | 219.9k $25.7m | Reduced -168.2k |
| VANGUARD FIDUCIARY TRUST CO 0.01% of their portfolio | 205.7k $24.0m | First filing |
| DEPRINCE RACE & ZOLLO INC 0.45% of their portfolio | 203.4k $23.8m | Reduced -860 |
| Bank of New York Mellon Corp 0.00% of their portfolio | 181.1k $21.2m | Added +6.8k |
| Invesco Ltd. 0.00% of their portfolio | 179.4k $21.0m | Reduced -33.8k |
| TEACHERS RETIREMENT SYSTEM OF THE STATE OF KENTUCKY 0.16% of their portfolio | 178.2k $20.8m | Added +12.8k |
| Ceredex Value Advisors LLC 0.65% of their portfolio | 177.9k $20.8m | Reduced -57.7k |
| Man Group plc 0.04% of their portfolio | 160.3k $18.7m | New |
| ROBOTTI ROBERT 2.64% of their portfolio | 145.0k $16.9m | Reduced -111.2k |
| CAPSTONE INVESTMENT ADVISORS, LLC 0.13% of their portfolio | 135.8k $15.9m | Added +132.7k |
| SPROTT INC. 0.47% of their portfolio | 132.6k $15.5m | Reduced -7.4k |
| Quantinno Capital Management LP 0.02% of their portfolio | 121.4k $14.2m | Added +5.1k |
| Recurrent Investment Advisors LLC 0.79% of their portfolio | 112.8k $13.2m | Added +37.2k |
| Yaupon Capital Management LP 0.62% of their portfolio | 107.0k $12.5m | New |
| WELLS FARGO & COMPANY/MN 0.00% of their portfolio | 106.7k $12.5m | Added +14.8k |
| JANE STREET GROUP, LLC 0.01% of their portfolio | 105.7k $12.3m | New |
| ROYAL BANK OF CANADA 0.00% of their portfolio | 104.0k $12.1m | Added +18.7k |
| FIRST TRUST ADVISORS LP 0.01% of their portfolio | 102.3k $12.0m | Reduced -44.1k |
| JPMORGAN CHASE & CO 0.00% of their portfolio | 97.7k $11.3m | Added +30.4k |
| Russell Investments Group, Ltd. 0.01% of their portfolio | 89.4k $10.4m | Reduced -69.0k |
| RHUMBLINE ADVISERS 0.01% of their portfolio | 87.3k $10.2m | Added +1.9k |
| MILLENNIUM MANAGEMENT LLC 0.01% of their portfolio | 85.0k $9.9m | Reduced -342.8k |
| Meiji Yasuda Asset Management Co Ltd. 0.46% of their portfolio | 79.5k $9.3m | New |
| Swiss National Bank 0.01% of their portfolio | 75.9k $8.9m | Unchanged |
| PDT Partners, LLC 0.52% of their portfolio | 75.8k $8.9m | Added +10.8k |
| PRINCIPAL FINANCIAL GROUP INC 0.00% of their portfolio | 74.5k $8.7m | Added +2.8k |
| Thomist Capital Management, LP 2.92% of their portfolio | 73.0k $8.5m | Reduced -38.9k |
| Cerity Partners LLC 0.01% of their portfolio | 72.7k $8.5m | Reduced -54.4k |
| AGMAN CAPITAL LLC 6.72% of their portfolio | 72.3k $8.4m | Unchanged |
| MACKENZIE FINANCIAL CORP 0.01% of their portfolio | 72.0k $8.4m | Added +52.1k |
| ALLIANCEBERNSTEIN L.P. 0.00% of their portfolio | 67.3k $5.0m | Reduced -1.1k |
| CAPITAL INTERNATIONAL SARL 0.12% of their portfolio | 63.6k $7.4m | New |
| Lloyd Harbor Capital Management, LLC 3.75% of their portfolio | 62.0k $7.2m | New |
| Rokos Capital Management LLP 0.13% of their portfolio | 60.8k $7.1m | New |
| Walleye Capital LLC 0.04% of their portfolio | 59.8k $7.0m | Added +12.2k |
| CITIGROUP INC 0.00% of their portfolio | 54.6k $6.4m | Added +27.2k |
| Legal & General Group Plc 0.00% of their portfolio | 50.7k $5.9m | Reduced -6.5k |
| Albar Capital Partners LLP 0.92% of their portfolio | 48.8k $5.7m | New |
| Tidal Investments LLC 0.02% of their portfolio | 47.8k $5.5m | New |
| VICTORY CAPITAL MANAGEMENT INC 0.00% of their portfolio | 45.6k $5.3m | Reduced -1.1m |
| Trek Financial, LLC 0.28% of their portfolio | 45.3k $5.3m | New |
| CALIFORNIA STATE TEACHERS RETIREMENT SYSTEM 0.01% of their portfolio | 44.5k $5.2m | Added +8.4k |
| OCCUDO QUANTITATIVE STRATEGIES LP 0.28% of their portfolio | 44.4k $5.1m | Added +19.2k |
| Engineers Gate Manager LP 0.06% of their portfolio | 42.5k $5.0m | Reduced -246.8k |
| BI Asset Management Fondsmaeglerselskab A/S 0.05% of their portfolio | 42.0k $4.9m | Added +35.0k |
| Retirement Systems of Alabama 0.02% of their portfolio | 40.9k $4.8m | Added +859 |
| BANK OF MONTREAL /CAN/ 0.00% of their portfolio | 39.0k $4.6m | Added +12.1k |
| Squarepoint Ops LLC 0.01% of their portfolio | 38.5k $4.5m | New |
| CAPITAL INTERNATIONAL LTD /CA/ 0.16% of their portfolio | 37.3k $4.4m | New |
| Twin Tree Management, LP 0.88% of their portfolio | 36.0k $4.2m | New |
| Corient Private Wealth LP 0.01% of their portfolio | 35.0k $4.1m | Reduced -66.5k |
| Gotham Asset Management, LLC 0.01% of their portfolio | 34.6k $4.0m | Added +25.4k |
| VANGUARD ASSET MANAGEMENT, Ltd 0.00% of their portfolio | 33.4k $3.9m | First filing |
| MANUFACTURERS LIFE INSURANCE COMPANY, THE 0.00% of their portfolio | 33.3k $3.9m | Reduced -156 |
| Boston Partners 0.00% of their portfolio | 31.7k $3.7m | New |
| Occam Crest Management LP 2.13% of their portfolio | 29.3k $3.4m | New |
| AMERIPRISE FINANCIAL INC 0.00% of their portfolio | 28.5k $3.3m | Reduced -20.6k |
| ENVESTNET ASSET MANAGEMENT INC 0.00% of their portfolio | 28.0k $3.3m | Added +176 |
| STATE OF WISCONSIN INVESTMENT BOARD 0.01% of their portfolio | 25.3k $2.9m | Reduced -459 |
| California Public Employees Retirement System 0.00% of their portfolio | 25.0k $2.9m | Reduced -21.8k |
| STIFEL FINANCIAL CORP 0.00% of their portfolio | 24.9k $2.9m | Added +6.0k |
| SG Americas Securities, LLC 0.00% of their portfolio | 24.6k $2.9m | Reduced -12.4k |
| STATE BOARD OF ADMINISTRATION OF FLORIDA RETIREMENT SYSTEM 0.01% of their portfolio | 24.1k $2.8m | Unchanged |
| Quantbot Technologies LP 0.11% of their portfolio | 23.9k $2.8m | Reduced -15.7k |