Estimated market cap $8.13BShares outstanding from the company’s latest SEC filing (all share classes, each priced at its own close; ADRs converted to ADS) × last close from Tiingo. Updated daily. This figure: shares as of Oct 28, 2026, last close Nov 13, 2026.127.89M shares, shares as of Oct 28, 2026CIK 1262823The SEC’s Central Index Key, the number it uses to identify every company and person that files.
Insider trades, 12 mo
0 buys · 9 sells
$10.19M sold, open market
Congress trades, 24 mo
—
No disclosed trades
13F holders
…
Lobbying, 12 mo
—
No lobbying filings
Federal contracts, 12 mo
—
None matched
Ask your AI:
Latest 10-Q
What changed in Westlake Corporation's latest quarterly report, compared with the one before.
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Insider trades
Open-market trades from Form 4. 10b5-1 marks a plan set in advance.Open-market buys and sales by officers, directors and 10% owners, from SEC Form 4. A plan set in advance is marked 10b5-1.
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13F holders
Funds that report this stock, checked against market prices.Fund managers with over $100 million in US-listed stocks file a 13F each quarter, up to 45 days after quarter end. Long positions only.
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Top 10 holders.Premium lists every holder, with CSV downloads.
Disclosed in dollar ranges, up to 45 days after the trade.Members of Congress, their spouses and dependent children report trades in dollar ranges, up to 45 days after the trade.
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Executive-branch trades
2 trades
Trades in Westlake Corporation reported by the President, Cabinet members and other senior executive-branch officials. Amounts are ranges.Form 278-T is the periodic transaction report that senior executive-branch officials file with the Office of Government Ethics. They must report each trade over $1,000 within 30 days of being notified of it, and no later than 45 days after the trade. Amounts are ranges, not exact figures.
Recent executive-branch trades
The form has no ticker column. The asset is shown as the filer wrote it. We add a ticker link only when we could match the asset to a listed company.
The form asks for a range, such as $1,001 - $15,000, not an exact amount. A line can be left blank when the filer's note says the amount was not more than $1,000.
What Westlake Corporation and its lobbying firms report each quarter.A company that lobbies with its own staff reports its expenses; a lobbying firm it hires reports the income it received. We count both.
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Institutional ownership over time
How many funds reported holding the stock at the end of each quarter, and how many shares they held between them.
13F holders, Q3 2026Fund managers with over $100 million in US-listed stocks file a 13F each quarter, up to 45 days after quarter end. Long positions only.
247
17.1% of shares · 85 added
Latest 10-Q
Q3 2026
What changed in Westlake Corporation's latest quarterly report, compared with the one before.
Filed Nov 4, 2026 · Quarter ended Sep 30, 2026
Summary text goes here once it has loaded. Summary text goes here once it has loaded.
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AI summary of changes vs the prior report. Written by AI from the paragraphs that changed, and checked against them. This is information, not investment advice.
Compared with the 10-Q for the quarter ended Jun 30, 2026. Sections compared: management's discussion, risk factors, legal proceedings and controls and procedures.
Open-market trades from Form 4. 10b5-1 marks a plan set in advance.Open-market buys and sales by officers, directors and 10% owners, from SEC Form 4. A plan set in advance is marked 10b5-1.
No open-market insider trades reported since Aug 11, 2026. Insiders have two business days to file.
Recent insider trades
How the stock has done since the trade date, measured against the S&P 500 over the same days. It describes the stock, not the trader's actual gain or loss.
247 funds report WLK. Values checked against market prices.Fund managers with over $100 million in US-listed stocks file a 13F each quarter, up to 45 days after quarter end. Long positions only.
Funds own 31% of shares (Q2 2026)Fund managers with more than $100 million in US-listed stocks file a 13F each quarter. It lists their long stock positions only (shorts, options and bonds are left out) and can arrive up to 45 days after the quarter ends, so this is a snapshot of the quarter end. We add up the shares every fund reports in this class and divide by the shares outstanding. The total can pass 100%: the same shares are often reported by more than one manager (an adviser and the fund it runs), lent shares can be reported twice, and the share count can be out of date after buybacks. We divided 39.79M reported shares by 127.80M shares, from the company’s SEC filing as of Jul 29, 2026.
360 funds hold the stock.
Q3 2026: 17% · 5,560 of ~8,900 funds reported so farFunds have 45 days after a quarter ends to file. This quarter’s reports are still arriving, so the figure only counts the funds that have filed so far and will usually rise.
Q2 202531%
Q3 202533%
Q4 202536%
Q1 202634%
Q2 202631%
Q3 2026 (so far)17%
Q3 2026. 40 new, 85 added to, 78 trimmed, 154 exited since Q2 2026.
Download CSVEvery fund that holds WLK, not only these ten. A download holds at most 10,000 rows; narrow the filters to get a smaller slice.
Trades by members of Congress
Disclosed in dollar ranges, up to 45 days after the trade.Members of Congress, their spouses and dependent children report trades in dollar ranges, up to 45 days after the trade.
Recent congressional trades
How the stock has done since the trade date, measured against the S&P 500 over the same days. It describes the stock, not the trader's actual gain or loss.
What Westlake Corporation and its lobbying firms report each quarter.A company that lobbies with its own staff reports its expenses; a lobbying firm it hires reports the income it received. We count both.
No recent lobbying filings for this company.
Institutional ownership over time
How many funds reported holding the stock at the end of each quarter, and how many shares they held between them.
Funds holding the stock
Shares they report, adjusted for splits
Funds holding the stock by quarter
Q2 2013
198
—
42.13M
$2.0B
Q3 2013
218
+20
40.11M
$2.1B
Q4 2013
228
+10
39.78M
$2.4B
Q1 2014
243
+15
38.36M
$2.5B
Q2 2014
267
+24
39.17M
$3.3B
Q3 2014
282
+15
38.27M
$3.3B
Q4 2014
278
-4
38.56M
$2.4B
Q1 2015
264
-14
39.37M
$2.8B
Q2 2015
261
-3
37.58M
$2.6B
Q3 2015
249
-12
37.68M
$2.0B
Q4 2015
270
+21
35.87M
$2.0B
Q1 2016
272
+2
39.36M
$1.8B
Q2 2016
237
-35
38.86M
$1.7B
Q3 2016
221
-16
38.21M
$2.0B
Q4 2016
224
+3
38.95M
$2.2B
Q1 2017
221
-3
39.72M
$2.6B
Q2 2017
217
-4
41.87M
$2.8B
Q3 2017
241
+24
40.21M
$3.3B
Q4 2017
282
+41
39.19M
$4.2B
Q1 2018
318
+36
39.00M
$4.3B
Q2 2018
329
+11
40.32M
$4.3B
Q3 2018
312
-17
39.71M
$3.3B
Q4 2018
300
-12
36.44M
$2.4B
Q1 2019
305
+5
36.85M
$2.5B
Q2 2019
268
-37
40.10M
$2.8B
Q3 2019
247
-21
39.75M
$2.6B
Q4 2019
250
+3
38.22M
$2.7B
Q1 2020
218
-32
39.71M
$1.5B
Q2 2020
220
+2
36.59M
$2.0B
Q3 2020
206
-14
35.05M
$2.2B
Q4 2020
225
+19
33.64M
$2.7B
Q1 2021
240
+15
34.76M
$3.1B
Q2 2021
276
+36
33.55M
$3.0B
Q3 2021
272
-4
34.51M
$3.1B
Q4 2021
297
+25
34.75M
$3.4B
Q1 2022
326
+29
36.16M
$4.5B
Q2 2022
354
+28
35.62M
$3.5B
Q3 2022
321
-33
35.46M
$3.1B
Q4 2022
344
+23
36.40M
$3.7B
Q1 2023
341
-3
42.64M
$4.9B
Q2 2023
340
-1
36.98M
$4.4B
Q3 2023
335
-5
37.26M
$4.6B
Q4 2023
357
+22
36.38M
$5.1B
Q1 2024
347
-10
35.54M
$5.4B
Q2 2024
381
+34
34.19M
$5.0B
Q3 2024
402
+21
33.90M
$5.1B
Q4 2024
377
-25
35.29M
$4.0B
Q1 2025
360
-17
36.40M
$3.6B
Q2 2025
305
-55
39.59M
$3.0B
Q3 2025
308
+3
42.39M
$3.3B
Q4 2025
300
-8
46.45M
$3.4B
Q1 2026
342
+42
44.11M
$5.1B
Q2 2026
360
+18
39.79M
$2.9B
Q3 2026
247
-113
21.86M
$1.4B
Each point is a quarter-end, from Q2 2013 to Q3 2026. A fund's 13F lists its long positions in US-listed securities as of the last day of the quarter and arrives up to 45 days later, so each point shows holdings at quarter-end, not on the day they were reported.
Common shares only; options and bonds are left out. When a fund amends a report, the amended version is the one counted.
The history follows the company's current CUSIP number (960413102). If the company's shares were ever re-issued under a different CUSIP, the quarters before the change are not part of this series, so the first point (Q2 2013) can be later than the stock's first appearance in 13F reports.
Share counts are adjusted for stock splits (2-for-1 on Mar 19, 2014): reports from before a split are multiplied by its ratio, so every quarter is on the share count of Q3 2026.
A quarter appears once our daily update has built its summary. If a summary cannot be built, older reports are kept and the chart shows the quarters it has until the next update repairs it.