Who owns ATI (ATI)
Which tracked institutional funds hold ATI, how they are positioned, and who is buying versus exiting — from SEC Form 13F-HR filings. See ATI company fundamentals →
Ownership as of the 2026-Q1 13F filings (latest filed 2026-05-18). 13F is disclosed up to 45 days after quarter-end, so the most recent quarter fills in over the following weeks.
How the tape is positioned
292 tracked funds added or opened ATI while 100 trimmed or exited it between 2025-Q4 and 2026-Q1 — the tape is split. When large holders disagree on a name, the funds moving first are sometimes ahead of the story.
A prompt to read the filings, not a verdict. 13F is a quarter-end snapshot disclosed up to 45 days late; a fund adds or exits for mandate, benchmark, and timing reasons that have nothing to do with a view on the stock. This is a starting question, not a signal to trade.
Conviction spread
ATI’s largest tracked holder by dollar value, BlackRock, Inc., sizes it at 0.1% of its own reported 13F book, while the median holder sizes it at 0.1% of theirs — a 0.0pp gap the other way — the median holder sizes ATI more heavily than its largest holder by dollar value does.
Book-share is each fund’s reported value in ATI divided by its whole reported 13F book, so it is comparable across funds of different sizes and is unaffected by stock splits. A higher share means a fund has committed more of its book to the name — a starting question about conviction, not a verdict or a signal to trade.
Institutional & insider positioning
Between 2025-Q4 and 2026-Q1, across 671 tracked filers holding ATI, 403 increased or opened the position and 254 reduced or closed it; over the same quarter, open-market insider Form 4 buying and selling roughly offset.
This fuses two public signals for the same quarter — how tracked institutions changed their positions and whether insiders bought or sold in the open market. It describes what was filed; it is a starting question, not a verdict or a signal to trade.
New buyers & exits
Funds opening or closing a position in ATI between the 2025-Q4 and 2026-Q1 13F filings, and the largest changes among funds holding it in both. New buyers and exits are counted on fund presence (split-invariant); adds and trims are measured on reported value.
New buyers 58
- VANGUARD CAPITAL MANAGEMENT LLC$891M
- VANGUARD PORTFOLIO MANAGEMENT LLC$847M
- VIKING GLOBAL INVESTORS LP$485M
- VANGUARD FIDUCIARY TRUST CO$123M
- Artemis Investment Management LLP$105M
- Freestone Grove Partners LP$84M
Full exits 34
- VANGUARD GROUP INC$1.5B
- MUFG Securities EMEA plc$32M
- Cartenna Capital, LP$30M
- CIBC WORLD MARKETS CORP$20M
- VOLORIDGE INVESTMENT MANAGEMENT, LLC$20M
- Concentric Capital Strategies, LP$19M
Largest adds
- Capital Research Global Investors$481M
- BlackRock, Inc.$299M
- Point72 Asset Management, L.P.$194M
- JANE STREET GROUP, LLC$185M
- FMR LLC$173M
- Invesco Ltd.$158M
Largest trims
- Capital International Investors$1.1B
- NORGES BANK$122M
- DENDUR CAPITAL LP$47M
- DIMENSIONAL FUND ADVISORS LP$45M
- Woodline Partners LP$41M
- FRONTIER CAPITAL MANAGEMENT CO LLC$40M
Institutional holders
One row per tracked fund, largest reported value first. “% of value” is the fund’s share of this security’s tracked institutional value — not of shares outstanding. Rows marked stale are from an earlier filing than the security’s latest quarter — that fund is absent from the newest snapshot (position exited, or reported under a different name).
| Fund | Shares | Reported value | % of value | Quarter |
|---|---|---|---|---|
| BlackRock, Inc. added | 18,708,922 | $3.7B | 17.1% | 2026-Q2 |
| Capital World Investors trimmed | 5,249,249 | $1.0B | 4.8% | 2026-Q2 |
| STATE STREET CORP trimmed | 5,237,299 | $1.0B | 4.8% | 2026-Q2 |
| Capital Research Global Investors trimmed | 5,093,768 | $1.0B | 4.7% | 2026-Q2 |
| FMR LLC trimmed | 4,989,171 | $983M | 4.6% | 2026-Q2 |
| VANGUARD CAPITAL MANAGEMENT LLC new | 6,124,128 | $891M | 4.1% | 2026-Q1 |
| VANGUARD PORTFOLIO MANAGEMENT LLC new | 5,821,508 | $847M | 3.9% | 2026-Q1 |
| Capital International Investors trimmed | 3,719,485 | $733M | 3.4% | 2026-Q2 |
| Invesco Ltd. trimmed | 3,449,291 | $680M | 3.2% | 2026-Q2 |
| GEODE CAPITAL MANAGEMENT, LLC added | 2,947,325 | $429M | 2.0% | 2026-Q1 |
| NORGES BANK added | 1,739,884 | $343M | 1.6% | 2026-Q2 |
| AQR CAPITAL MANAGEMENT LLC added | 1,432,935 | $282M | 1.3% | 2026-Q2 |
| Point72 Asset Management, L.P. trimmed | 1,240,348 | $244M | 1.1% | 2026-Q2 |
| MORGAN STANLEY added | 1,668,591 | $243M | 1.1% | 2026-Q1 |
| VIKING GLOBAL INVESTORS LP trimmed | 1,153,880 | $227M | 1.1% | 2026-Q2 |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC added | 1,502,129 | $218M | 1.0% | 2026-Q1 |
| JANE STREET GROUP, LLC added | 1,491,263 | $217M | 1.0% | 2026-Q1 |
| UBS Group AG added | 1,419,080 | $206M | 1.0% | 2026-Q1 |
| PRICE T ROWE ASSOCIATES INC /MD/ added | 1,021,799 | $201M | 0.9% | 2026-Q2 |
| DIMENSIONAL FUND ADVISORS LP trimmed | 1,366,804 | $199M | 0.9% | 2026-Q1 |
| BANK OF AMERICA CORP /DE/ added | 1,364,941 | $199M | 0.9% | 2026-Q1 |
| DENDUR CAPITAL LP trimmed | 1,283,103 | $187M | 0.9% | 2026-Q1 |
| NORTHERN TRUST CORP added | 1,239,020 | $180M | 0.8% | 2026-Q1 |
| ARROWSTREET CAPITAL, LIMITED PARTNERSHIP added | 1,203,726 | $175M | 0.8% | 2026-Q1 |
| MILLENNIUM MANAGEMENT LLC added | 875,260 | $173M | 0.8% | 2026-Q2 |
| POLEN CAPITAL MANAGEMENT LLC new | 819,236 | $161M | 0.7% | 2026-Q2 |
| D. E. Shaw & Co., Inc. trimmed | 815,585 | $161M | 0.7% | 2026-Q2 |
| Holocene Advisors, LP added | 1,097,588 | $160M | 0.7% | 2026-Q1 |
| SG Americas Securities, LLC added | 1,075,368 | $156M | 0.7% | 2026-Q1 |
| AMERICAN CENTURY COMPANIES INC trimmed | 1,069,282 | $156M | 0.7% | 2026-Q1 |
| BOWEN HANES & CO INC trimmed | 1,043,105 | $152M | 0.7% | 2026-Q1 |
| MIRAE ASSET GLOBAL ETFS HOLDINGS Ltd. added | 1,032,774 | $150M | 0.7% | 2026-Q1 |
| AMERIPRISE FINANCIAL INC trimmed | 998,834 | $145M | 0.7% | 2026-Q1 |
| MARSHALL WACE, LLP added | 709,552 | $140M | 0.6% | 2026-Q2 |
| Fisher Asset Management, LLC added | 924,521 | $134M | 0.6% | 2026-Q1 |
| Bank of New York Mellon Corp trimmed | 869,184 | $126M | 0.6% | 2026-Q1 |
| TWO SIGMA INVESTMENTS, LP added | 636,671 | $125M | 0.6% | 2026-Q2 |
| Qube Research & Technologies Ltd added | 858,818 | $125M | 0.6% | 2026-Q1 |
| VANGUARD FIDUCIARY TRUST CO new | 844,377 | $123M | 0.6% | 2026-Q1 |
| PNC FINANCIAL SERVICES GROUP, INC. added | 831,736 | $121M | 0.6% | 2026-Q1 |
| PRUDENTIAL FINANCIAL INC added | 809,970 | $118M | 0.5% | 2026-Q1 |
| BARROW HANLEY MEWHINNEY & STRAUSS LLC trimmed | 782,466 | $114M | 0.5% | 2026-Q1 |
| Artemis Investment Management LLP added | 721,505 | $105M | 0.5% | 2026-Q1 |
| BALYASNY ASSET MANAGEMENT L.P. trimmed | 514,088 | $101M | 0.5% | 2026-Q2 |
| FRONTIER CAPITAL MANAGEMENT CO LLC trimmed | 694,422 | $101M | 0.5% | 2026-Q1 |
| CITADEL ADVISORS LLC added | 497,418 | $98M | 0.5% | 2026-Q2 |
| LOOMIS SAYLES & CO L P trimmed | 653,416 | $95M | 0.4% | 2026-Q1 |
| BNP PARIBAS FINANCIAL MARKETS added | 651,996 | $95M | 0.4% | 2026-Q1 |
| RAYMOND JAMES FINANCIAL INC trimmed | 638,706 | $92M | 0.4% | 2026-Q1 |
| Assenagon Asset Management S.A. added | 584,030 | $85M | 0.4% | 2026-Q1 |
| Nuveen, LLC added | 578,616 | $84M | 0.4% | 2026-Q1 |
| Freestone Grove Partners LP added | 575,873 | $84M | 0.4% | 2026-Q1 |
| FEDERATED HERMES, INC. trimmed | 545,532 | $79M | 0.4% | 2026-Q1 |
| Allspring Global Investments Holdings, LLC trimmed | 520,246 | $79M | 0.4% | 2026-Q1 |
| NEUBERGER BERMAN GROUP LLC trimmed | 494,925 | $72M | 0.3% | 2026-Q1 |
| BANK OF NOVA SCOTIA added | 467,149 | $68M | 0.3% | 2026-Q1 |
| ALLIANCEBERNSTEIN L.P. added | 575,528 | $66M | 0.3% | 2026-Q1 |
| GOLDMAN SACHS GROUP INC added | 447,819 | $65M | 0.3% | 2026-Q1 |
| VAUGHAN NELSON INVESTMENT MANAGEMENT, L.P. added | 382,375 | $56M | 0.3% | 2026-Q1 |
| JPMORGAN CHASE & CO added | 407,423 | $55M | 0.3% | 2026-Q1 |
| SEGALL BRYANT & HAMILL, LLC added | 350,055 | $55M | 0.3% | 2026-Q1 |
| ING GROEP NV added | 377,500 | $55M | 0.3% | 2026-Q1 |
| SCHRODER INVESTMENT MANAGEMENT GROUP trimmed | 402,593 | $55M | 0.3% | 2026-Q1 |
| Square Wave Capital, LLC new | 366,400 | $53M | 0.2% | 2026-Q1 |
| GAMCO INVESTORS, INC. ET AL trimmed | 361,500 | $53M | 0.2% | 2026-Q1 |
| UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC added | 354,737 | $52M | 0.2% | 2026-Q1 |
| RHUMBLINE ADVISERS added | 354,371 | $52M | 0.2% | 2026-Q1 |
| WELLS FARGO & COMPANY/MN added | 351,142 | $51M | 0.2% | 2026-Q1 |
| JUPITER ASSET MANAGEMENT LTD added | 341,677 | $50M | 0.2% | 2026-Q1 |
| Retirement Systems of Alabama added | 312,287 | $45M | 0.2% | 2026-Q1 |
| PRINCIPAL FINANCIAL GROUP INC added | 303,158 | $44M | 0.2% | 2026-Q1 |
| Swiss National Bank trimmed | 268,800 | $39M | 0.2% | 2026-Q1 |
| Allianz Asset Management GmbH added | 267,834 | $39M | 0.2% | 2026-Q1 |
| Jain Global LLC trimmed | 264,476 | $38M | 0.2% | 2026-Q1 |
| KLCM Advisors, Inc. trimmed | 262,839 | $38M | 0.2% | 2026-Q1 |
| Amundi added | 261,186 | $38M | 0.2% | 2026-Q1 |
| Gotham Asset Management, LLC trimmed | 260,488 | $38M | 0.2% | 2026-Q1 |
| California Public Employees Retirement System trimmed | 253,797 | $37M | 0.2% | 2026-Q1 |
| HRT FINANCIAL LP added | 252,898 | $37M | 0.2% | 2026-Q1 |
| Schonfeld Strategic Advisors LLC added | 177,751 | $35M | 0.2% | 2026-Q2 |
| BLAIR WILLIAM & CO/IL added | 236,996 | $34M | 0.2% | 2026-Q1 |
| Capital International, Inc./CA/ trimmed | 234,928 | $34M | 0.2% | 2026-Q1 |
| ENVESTNET ASSET MANAGEMENT INC added | 215,778 | $31M | 0.1% | 2026-Q1 |
| Driehaus Capital Management LLC trimmed | 212,734 | $31M | 0.1% | 2026-Q1 |
| Legal & General Group Plc trimmed | 211,998 | $31M | 0.1% | 2026-Q1 |
| STATE OF WISCONSIN INVESTMENT BOARD trimmed | 201,963 | $29M | 0.1% | 2026-Q1 |
| TUDOR INVESTMENT CORP ET AL added | 148,638 | $29M | 0.1% | 2026-Q2 |
| HAWK RIDGE CAPITAL MANAGEMENT LP trimmed | 185,600 | $27M | 0.1% | 2026-Q1 |
| Aventail Capital Group, LP new | 185,312 | $27M | 0.1% | 2026-Q1 |
| LORD, ABBETT & CO. LLC trimmed | 182,049 | $26M | 0.1% | 2026-Q1 |
| EMERALD ADVISERS, LLC trimmed | 181,485 | $26M | 0.1% | 2026-Q1 |
| VANGUARD GROUP INC trimmed | 12,726,524 | $1.5B | 6.8% | 2025-Q4 stale |
| Palestra Capital Management LLC new | 1,062,298 | $92M | 0.4% | 2025-Q2 stale |
| FULLER & THALER ASSET MANAGEMENT, INC. added | 911,108 | $79M | 0.4% | 2025-Q2 stale |
| Castle Hook Partners LP new | 744,648 | $64M | 0.3% | 2025-Q2 stale |
| NorthRock Partners, LLC trimmed | 540,447 | $47M | 0.2% | 2025-Q2 stale |
| Forest Avenue Capital Management LP trimmed | 492,976 | $43M | 0.2% | 2025-Q2 stale |
| MUFG Securities EMEA plc new | 277,000 | $32M | 0.1% | 2025-Q4 stale |
| Cartenna Capital, LP trimmed | 260,000 | $30M | 0.1% | 2025-Q4 stale |
| Cubist Systematic Strategies, LLC added | 335,884 | $29M | 0.1% | 2025-Q2 stale |
Ownership over time
Tracked institutional holder count and total shares held by filing quarter (independent scales). The curated-era tail and any mid-ingest latest quarter are handled honestly — a partial quarter is not drawn as a collapse.
Reading this table
Funds hold the same stock for different reasons — an index fund “holds” almost everything, an active manager sizes a name to a mandate and a benchmark, and each fund entered at its own price and time. Because 13F is filed up to 45 days after quarter-end, every row is a backward-looking snapshot; a manager may have traded since. Share-class siblings (a company’s A and C shares) are rolled up to one line so a dual-class name is never double-counted. Compare like-for-like. A large holder is not an endorsement, and a fund exiting is not a warning — this is a starting question, not a verdict.
About 13F filings
A Form 13F is a quarterly disclosure that institutional investment managers with over $100 million in US-listed equities must file with the SEC. In plain English: it is a snapshot of the long stock positions a fund held at the end of a quarter. It covers long US-listed equities only — not short positions, options, cash, or private holdings — and the funds shown are the large sample we track, not the complete 13F universe.