Who owns ATMU (ATMU)
Which tracked institutional funds hold ATMU, how they are positioned, and who is buying versus exiting — from SEC Form 13F-HR filings. See ATMU company fundamentals →
Ownership as of the 2026-Q1 13F filings. 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
120 tracked funds added or opened ATMU while 58 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
ATMU’s largest tracked holder by dollar value, VANGUARD GROUP INC, sizes it at 0.0% of its own reported 13F book, while the median holder sizes it at 0.0% of theirs — a 0.0pp gap the other way — the median holder sizes ATMU more heavily than its largest holder by dollar value does.
Book-share is each fund’s reported value in ATMU 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 351 tracked filers holding ATMU, 198 increased or opened the position and 139 reduced or closed it; over the same quarter, there were no open-market insider Form 4s.
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 ATMU 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 31
- VANGUARD PORTFOLIO MANAGEMENT LLC$209M
- VANGUARD CAPITAL MANAGEMENT LLC$202M
- VANGUARD FIDUCIARY TRUST CO$32M
- NOMURA ASSET MANAGEMENT INTERNATIONAL INC.$16M
- Tidal Investments LLC$7M
- CASTLEARK MANAGEMENT LLC$7M
Full exits 15
- VANGUARD GROUP INC$402M
- Trexquant Investment LP$7M
- Yost Capital Management, LP$6M
- NEOS Investment Management LLC$5M
- Verition Fund Management LLC$4M
- Ionic Capital Management LLC$3M
Largest adds
- T. Rowe Price Investment Management, Inc.$87M
- NEUBERGER BERMAN GROUP LLC$66M
- FMR LLC$43M
- Invesco Ltd.$40M
- ARROWSTREET CAPITAL, LIMITED PARTNERSHIP$39M
- Qube Research & Technologies Ltd$25M
Largest trims
- EMINENCE CAPITAL, LP$126M
- BlackRock, Inc.$35M
- Allspring Global Investments Holdings, LLC$24M
- Assenagon Asset Management S.A.$23M
- Parsifal Capital Management, LP$19M
- Medina Value Partners, LLC$14M
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. trimmed | 5,568,682 | $316M | 6.4% | 2026-Q1 |
| FMR LLC added | 4,791,411 | $272M | 5.5% | 2026-Q1 |
| PRICE T ROWE ASSOCIATES INC /MD/ trimmed | 4,486,690 | $255M | 5.2% | 2026-Q1 |
| VANGUARD PORTFOLIO MANAGEMENT LLC new | 3,689,470 | $209M | 4.3% | 2026-Q1 |
| VANGUARD CAPITAL MANAGEMENT LLC new | 3,566,486 | $202M | 4.1% | 2026-Q1 |
| GOLDMAN SACHS GROUP INC added | 3,290,936 | $187M | 3.8% | 2026-Q1 |
| Invesco Ltd. added | 3,200,628 | $182M | 3.7% | 2026-Q1 |
| GEODE CAPITAL MANAGEMENT, LLC added | 2,645,085 | $150M | 3.0% | 2026-Q1 |
| FIRST TRUST ADVISORS LP added | 2,202,816 | $125M | 2.5% | 2026-Q1 |
| STATE STREET CORP trimmed | 1,895,114 | $108M | 2.2% | 2026-Q1 |
| MORGAN STANLEY trimmed | 1,736,994 | $99M | 2.0% | 2026-Q1 |
| D. E. Shaw & Co., Inc. added | 1,620,752 | $92M | 1.9% | 2026-Q1 |
| T. Rowe Price Investment Management, Inc. added | 1,580,676 | $90M | 1.8% | 2026-Q1 |
| JANUS HENDERSON GROUP PLC added | 1,551,117 | $88M | 1.8% | 2026-Q1 |
| Nuveen, LLC added | 1,444,750 | $82M | 1.7% | 2026-Q1 |
| WELLINGTON MANAGEMENT GROUP LLP trimmed | 1,386,421 | $79M | 1.6% | 2026-Q1 |
| Channing Capital Management, LLC trimmed | 1,385,924 | $79M | 1.6% | 2026-Q1 |
| MANGROVE PARTNERS IM, LLC | 1,315,227 | $75M | 1.5% | 2026-Q1 |
| DIMENSIONAL FUND ADVISORS LP added | 1,302,972 | $74M | 1.5% | 2026-Q1 |
| EMINENCE CAPITAL, LP trimmed | 1,281,995 | $73M | 1.5% | 2026-Q1 |
| WESTWOOD HOLDINGS GROUP INC trimmed | 1,239,186 | $70M | 1.4% | 2026-Q1 |
| NEUBERGER BERMAN GROUP LLC added | 1,174,210 | $67M | 1.4% | 2026-Q1 |
| ARROWSTREET CAPITAL, LIMITED PARTNERSHIP added | 999,548 | $57M | 1.2% | 2026-Q1 |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC added | 940,625 | $53M | 1.1% | 2026-Q1 |
| Port Capital LLC added | 908,680 | $52M | 1.0% | 2026-Q1 |
| BANK OF AMERICA CORP /DE/ added | 893,577 | $51M | 1.0% | 2026-Q1 |
| MASSACHUSETTS FINANCIAL SERVICES CO /MA/ trimmed | 818,850 | $50M | 1.0% | 2026-Q1 |
| RAYMOND JAMES FINANCIAL INC trimmed | 821,724 | $45M | 0.9% | 2026-Q1 |
| Parsifal Capital Management, LP trimmed | 788,987 | $45M | 0.9% | 2026-Q1 |
| ROYCE & ASSOCIATES LP added | 777,735 | $44M | 0.9% | 2026-Q1 |
| MANUFACTURERS LIFE INSURANCE COMPANY, THE trimmed | 758,807 | $43M | 0.9% | 2026-Q1 |
| Boston Trust Walden Corp trimmed | 750,579 | $43M | 0.9% | 2026-Q1 |
| FRONTIER CAPITAL MANAGEMENT CO LLC added | 742,221 | $42M | 0.9% | 2026-Q1 |
| Qube Research & Technologies Ltd added | 741,198 | $42M | 0.9% | 2026-Q1 |
| SILVERCREST ASSET MANAGEMENT GROUP LLC trimmed | 740,647 | $42M | 0.9% | 2026-Q1 |
| NORTHERN TRUST CORP added | 726,506 | $41M | 0.8% | 2026-Q1 |
| VANGUARD FIDUCIARY TRUST CO new | 564,188 | $32M | 0.7% | 2026-Q1 |
| ALGERT GLOBAL LLC trimmed | 514,932 | $29M | 0.6% | 2026-Q1 |
| FEDERATED HERMES, INC. added | 487,289 | $28M | 0.6% | 2026-Q1 |
| TEACHER RETIREMENT SYSTEM OF TEXAS trimmed | 474,416 | $27M | 0.5% | 2026-Q1 |
| JPMORGAN CHASE & CO added | 481,470 | $26M | 0.5% | 2026-Q1 |
| HEALTHCARE OF ONTARIO PENSION PLAN TRUST FUND added | 454,638 | $26M | 0.5% | 2026-Q1 |
| GW&K Investment Management, LLC trimmed | 439,199 | $25M | 0.5% | 2026-Q1 |
| JANE STREET GROUP, LLC added | 426,622 | $24M | 0.5% | 2026-Q1 |
| WILLIAM BLAIR INVESTMENT MANAGEMENT, LLC trimmed | 426,072 | $24M | 0.5% | 2026-Q1 |
| UBS Group AG added | 381,676 | $22M | 0.4% | 2026-Q1 |
| Aberdeen Group plc trimmed | 372,794 | $21M | 0.4% | 2026-Q1 |
| NEW YORK STATE COMMON RETIREMENT FUND trimmed | 362,222 | $21M | 0.4% | 2026-Q1 |
| Bank of New York Mellon Corp added | 359,696 | $20M | 0.4% | 2026-Q1 |
| Woodline Partners LP added | 355,936 | $20M | 0.4% | 2026-Q1 |
| SUSQUEHANNA INTERNATIONAL GROUP, LLP trimmed | 339,083 | $19M | 0.4% | 2026-Q1 |
| MARSHALL WACE, LLP trimmed | 322,609 | $18M | 0.4% | 2026-Q1 |
| BARCLAYS PLC added | 308,725 | $18M | 0.4% | 2026-Q1 |
| LOOMIS SAYLES & CO L P trimmed | 292,366 | $17M | 0.3% | 2026-Q1 |
| Schonfeld Strategic Advisors LLC trimmed | 286,704 | $16M | 0.3% | 2026-Q1 |
| NOMURA ASSET MANAGEMENT INTERNATIONAL INC. new | 284,198 | $16M | 0.3% | 2026-Q1 |
| DEUTSCHE BANK AG\ added | 283,401 | $16M | 0.3% | 2026-Q1 |
| VICTORY CAPITAL MANAGEMENT INC trimmed | 282,255 | $16M | 0.3% | 2026-Q1 |
| KENNEDY CAPITAL MANAGEMENT LLC trimmed | 275,231 | $16M | 0.3% | 2026-Q1 |
| AMERIPRISE FINANCIAL INC trimmed | 265,902 | $15M | 0.3% | 2026-Q1 |
| Allspring Global Investments Holdings, LLC trimmed | 257,251 | $15M | 0.3% | 2026-Q1 |
| ALTRINSIC GLOBAL ADVISORS LLC trimmed | 234,723 | $13M | 0.3% | 2026-Q1 |
| CITADEL ADVISORS LLC added | 230,465 | $13M | 0.3% | 2026-Q1 |
| Medina Value Partners, LLC trimmed | 226,439 | $13M | 0.3% | 2026-Q1 |
| Russell Investments Group, Ltd. trimmed | 208,549 | $12M | 0.2% | 2026-Q1 |
| PANAGORA ASSET MANAGEMENT INC added | 204,206 | $12M | 0.2% | 2026-Q1 |
| AXIOM INVESTORS LLC /DE trimmed | 203,670 | $12M | 0.2% | 2026-Q1 |
| Ancora Advisors LLC trimmed | 203,289 | $12M | 0.2% | 2026-Q1 |
| Assenagon Asset Management S.A. trimmed | 181,867 | $10M | 0.2% | 2026-Q1 |
| VOLORIDGE INVESTMENT MANAGEMENT, LLC trimmed | 167,596 | $10M | 0.2% | 2026-Q1 |
| SEI INVESTMENTS CO added | 164,150 | $9M | 0.2% | 2026-Q1 |
| Swiss National Bank trimmed | 161,249 | $9M | 0.2% | 2026-Q1 |
| AMERICAN CENTURY COMPANIES INC added | 161,147 | $9M | 0.2% | 2026-Q1 |
| HOTCHKIS & WILEY CAPITAL MANAGEMENT LLC trimmed | 158,026 | $9M | 0.2% | 2026-Q1 |
| Vest Financial, LLC added | 145,861 | $8M | 0.2% | 2026-Q1 |
| OP Asset Management Ltd added | 122,340 | $8M | 0.2% | 2026-Q1 |
| ACADIAN ASSET MANAGEMENT LLC added | 139,651 | $8M | 0.2% | 2026-Q1 |
| UBS AM, a distinct business unit of UBS ASSET MANAGEMENT AMERICAS LLC added | 133,897 | $8M | 0.2% | 2026-Q1 |
| PRUDENTIAL FINANCIAL INC trimmed | 129,955 | $7M | 0.1% | 2026-Q1 |
| Tidal Investments LLC added | 120,572 | $7M | 0.1% | 2026-Q1 |
| CASTLEARK MANAGEMENT LLC new | 119,350 | $7M | 0.1% | 2026-Q1 |
| MILLENNIUM MANAGEMENT LLC added | 118,637 | $7M | 0.1% | 2026-Q1 |
| DARK FOREST CAPITAL MANAGEMENT LP trimmed | 116,279 | $7M | 0.1% | 2026-Q1 |
| BAR HARBOR WEALTH MANAGEMENT added | 115,603 | $7M | 0.1% | 2026-Q1 |
| WELLS FARGO & COMPANY/MN trimmed | 115,512 | $7M | 0.1% | 2026-Q1 |
| Susquehanna Portfolio Strategies, LLC | 114,685 | $7M | 0.1% | 2026-Q1 |
| AQR CAPITAL MANAGEMENT LLC added | 108,784 | $6M | 0.1% | 2026-Q1 |
| PRENTISS SMITH & CO INC trimmed | 106,664 | $6M | 0.1% | 2026-Q1 |
| RHUMBLINE ADVISERS trimmed | 104,651 | $6M | 0.1% | 2026-Q1 |
| Livforsakringsbolaget Skandia, Omsesidigt added | 103,500 | $6M | 0.1% | 2026-Q1 |
| Tema ETFs LLC added | 101,957 | $6M | 0.1% | 2026-Q1 |
| VANGUARD GROUP INC trimmed | 7,736,046 | $402M | 8.2% | 2025-Q4 stale |
| Boston Partners trimmed | 586,400 | $26M | 0.5% | 2025-Q3 stale |
| FIL Ltd trimmed | 552,771 | $20M | 0.4% | 2025-Q1 stale |
| HAWK RIDGE CAPITAL MANAGEMENT LP added | 434,800 | $16M | 0.3% | 2025-Q2 stale |
| Driehaus Capital Management LLC trimmed | 397,909 | $15M | 0.3% | 2025-Q1 stale |
| BALYASNY ASSET MANAGEMENT L.P. trimmed | 310,826 | $14M | 0.3% | 2025-Q3 stale |
| Bayberry Capital Partners LP trimmed | 282,500 | $13M | 0.3% | 2025-Q3 stale |
| Trexquant Investment LP trimmed | 133,698 | $7M | 0.1% | 2025-Q4 stale |
| Watchtower Advisors, LP trimmed | 166,932 | $6M | 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.