Who owns ATS (ATS)
Which tracked institutional funds hold ATS, how they are positioned, and who is buying versus exiting — from SEC Form 13F-HR filings. See ATS 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
44 tracked funds added or opened ATS while 28 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
ATS’s largest tracked holder by dollar value, MASON CAPITAL MANAGEMENT LLC, sizes it at 75.5% of its own reported 13F book, while the median holder sizes it at 0.0% of theirs — a 75.4pp conviction gap — its largest holder concentrates the name more heavily than the typical one.
Book-share is each fund’s reported value in ATS 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 130 tracked filers holding ATS, 69 increased or opened the position and 53 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 ATS 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 12
- VANGUARD CAPITAL MANAGEMENT LLC$67M
- Vinva Investment Management Ltd$37M
- VANGUARD FIDUCIARY TRUST CO$21M
- Vanguard Global Advisers, LLC$7M
- Waratah Capital Advisors Ltd.$6M
- ArrowMark Colorado Holdings LLC$5M
Full exits 8
- VANGUARD GROUP INC$64M
- HEALTHCARE OF ONTARIO PENSION PLAN TRUST FUND$21M
- AGF MANAGEMENT LTD$11M
- Polar Asset Management Partners Inc.$5M
- MILLENNIUM MANAGEMENT LLC$2M
- AYAL Capital Advisors Ltd$2M
Largest adds
- TURTLE CREEK ASSET MANAGEMENT INC.$137M
- FIL Ltd$49M
- JANUS HENDERSON GROUP PLC$41M
- MASON CAPITAL MANAGEMENT LLC$34M
- TD Waterhouse Canada Inc.$20M
- EdgePoint Investment Group Inc.$12M
Largest trims
- Invesco Ltd.$26M
- 1832 Asset Management L.P.$11M
- Alberta Investment Management Corp$10M
- MIRAE ASSET GLOBAL ETFS HOLDINGS Ltd.$10M
- Beutel, Goodman & Co Ltd.$8M
- PRINCIPAL FINANCIAL GROUP INC$7M
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 |
|---|---|---|---|---|
| MASON CAPITAL MANAGEMENT LLC added | 16,404,170 | $463M | 16.2% | 2026-Q1 |
| TURTLE CREEK ASSET MANAGEMENT INC. added | 10,385,819 | $293M | 10.3% | 2026-Q1 |
| ROYAL BANK OF CANADA added | 7,761,838 | $219M | 7.7% | 2026-Q1 |
| EdgePoint Investment Group Inc. added | 7,168,112 | $202M | 7.1% | 2026-Q1 |
| Beutel, Goodman & Co Ltd. trimmed | 5,454,749 | $153M | 5.4% | 2026-Q1 |
| BANK OF MONTREAL /CAN/ added | 3,115,360 | $88M | 3.1% | 2026-Q1 |
| FAIRFAX FINANCIAL HOLDINGS LTD/ CAN | 2,486,400 | $69M | 2.4% | 2026-Q1 |
| VANGUARD CAPITAL MANAGEMENT LLC new | 2,366,730 | $67M | 2.3% | 2026-Q1 |
| JANUS HENDERSON GROUP PLC added | 2,297,214 | $65M | 2.3% | 2026-Q1 |
| Connor, Clark & Lunn Investment Management Ltd. trimmed | 2,264,757 | $64M | 2.2% | 2026-Q1 |
| FMR LLC added | 2,249,541 | $63M | 2.2% | 2026-Q1 |
| ACK Asset Management LLC | 1,846,196 | $52M | 1.8% | 2026-Q1 |
| FIL Ltd added | 1,778,181 | $50M | 1.8% | 2026-Q1 |
| TD Waterhouse Canada Inc. added | 1,634,449 | $47M | 1.6% | 2026-Q1 |
| Hill City Capital, LP | 1,649,857 | $47M | 1.6% | 2026-Q1 |
| TD Asset Management Inc added | 1,422,459 | $40M | 1.4% | 2026-Q1 |
| Vinva Investment Management Ltd new | 2,088,947 | $37M | 1.3% | 2026-Q1 |
| VAN LANSCHOT KEMPEN INVESTMENT MANAGEMENT N.V. added | 863,486 | $34M | 1.2% | 2026-Q1 |
| Scheer, Rowlett & Associates Investment Management Ltd. trimmed | 1,181,937 | $33M | 1.2% | 2026-Q1 |
| Clearbridge Investments, LLC trimmed | 1,091,291 | $31M | 1.1% | 2026-Q1 |
| Marathon Asset Management Ltd trimmed | 1,093,911 | $31M | 1.1% | 2026-Q1 |
| BANK OF AMERICA CORP /DE/ trimmed | 945,875 | $27M | 0.9% | 2026-Q1 |
| Alberta Investment Management Corp trimmed | 940,191 | $27M | 0.9% | 2026-Q1 |
| NORGES BANK trimmed | 1,027,456 | $26M | 0.9% | 2026-Q1 |
| MIRAE ASSET GLOBAL ETFS HOLDINGS Ltd. trimmed | 758,313 | $21M | 0.7% | 2026-Q1 |
| MASSACHUSETTS FINANCIAL SERVICES CO /MA/ trimmed | 533,957 | $21M | 0.7% | 2026-Q1 |
| VANGUARD FIDUCIARY TRUST CO new | 728,058 | $21M | 0.7% | 2026-Q1 |
| NATIONAL BANK OF CANADA /FI/ added | 648,282 | $18M | 0.6% | 2026-Q1 |
| PRINCIPAL FINANCIAL GROUP INC trimmed | 620,840 | $17M | 0.6% | 2026-Q1 |
| MACKENZIE FINANCIAL CORP trimmed | 616,504 | $17M | 0.6% | 2026-Q1 |
| Legal & General Group Plc added | 611,689 | $17M | 0.6% | 2026-Q1 |
| 1832 Asset Management L.P. trimmed | 401,696 | $11M | 0.4% | 2026-Q1 |
| Public Sector Pension Investment Board added | 356,837 | $10M | 0.4% | 2026-Q1 |
| CIBC WORLD MARKET INC. trimmed | 346,606 | $10M | 0.3% | 2026-Q1 |
| Invesco Ltd. trimmed | 306,927 | $9M | 0.3% | 2026-Q1 |
| Front Street Capital Management, Inc. trimmed | 261,088 | $7M | 0.3% | 2026-Q1 |
| Vanguard Global Advisers, LLC new | 258,998 | $7M | 0.3% | 2026-Q1 |
| Van Berkom & Associates Inc. trimmed | 257,360 | $7M | 0.3% | 2026-Q1 |
| FRANKLIN RESOURCES INC added | 247,467 | $7M | 0.2% | 2026-Q1 |
| CHARLES SCHWAB INVESTMENT MANAGEMENT INC added | 238,654 | $7M | 0.2% | 2026-Q1 |
| UBS Group AG trimmed | 227,628 | $6M | 0.2% | 2026-Q1 |
| Waratah Capital Advisors Ltd. added | 223,983 | $6M | 0.2% | 2026-Q1 |
| Dixon Mitchell Investment Counsel Inc. | 211,025 | $6M | 0.2% | 2026-Q1 |
| SCOTIA CAPITAL INC. trimmed | 192,530 | $5M | 0.2% | 2026-Q1 |
| Focus Partners Wealth | 181,975 | $5M | 0.2% | 2026-Q1 |
| ROYCE & ASSOCIATES LP added | 179,500 | $5M | 0.2% | 2026-Q1 |
| ArrowMark Colorado Holdings LLC new | 174,000 | $5M | 0.2% | 2026-Q1 |
| Granite Investment Partners, LLC trimmed | 173,031 | $5M | 0.2% | 2026-Q1 |
| MONTRUSCO BOLTON INVESTMENTS INC. trimmed | 170,956 | $5M | 0.2% | 2026-Q1 |
| SEI INVESTMENTS CO added | 167,820 | $5M | 0.2% | 2026-Q1 |
| Swiss National Bank | 164,400 | $5M | 0.2% | 2026-Q1 |
| FIRST TRUST ADVISORS LP trimmed | 154,403 | $4M | 0.2% | 2026-Q1 |
| Candelo Capital Management LP added | 151,688 | $4M | 0.1% | 2026-Q1 |
| CIBC Asset Management Inc added | 134,186 | $4M | 0.1% | 2026-Q1 |
| DIMENSIONAL FUND ADVISORS LP added | 122,456 | $3M | 0.1% | 2026-Q1 |
| Federation des caisses Desjardins du Quebec trimmed | 113,047 | $3M | 0.1% | 2026-Q1 |
| HARBOR CAPITAL ADVISORS, INC. new | 103,168 | $3M | 0.1% | 2026-Q1 |
| MORGAN STANLEY added | 100,390 | $3M | 0.1% | 2026-Q1 |
| TORONTO DOMINION BANK added | 93,175 | $3M | 0.1% | 2026-Q1 |
| Canoe Financial LP added | 87,430 | $2M | 0.1% | 2026-Q1 |
| LOUISBOURG INVESTMENTS INC. trimmed | 84,855 | $2M | 0.1% | 2026-Q1 |
| JANE STREET GROUP, LLC added | 82,641 | $2M | 0.1% | 2026-Q1 |
| CITADEL ADVISORS LLC trimmed | 81,239 | $2M | 0.1% | 2026-Q1 |
| MANUFACTURERS LIFE INSURANCE COMPANY, THE trimmed | 74,130 | $2M | 0.1% | 2026-Q1 |
| BRITISH COLUMBIA INVESTMENT MANAGEMENT Corp added | 70,422 | $2M | 0.1% | 2026-Q1 |
| GEODE CAPITAL MANAGEMENT, LLC added | 68,798 | $2M | 0.1% | 2026-Q1 |
| LAZARD ASSET MANAGEMENT LLC added | 69,912 | $2M | 0.1% | 2026-Q1 |
| VANGUARD ASSET MANAGEMENT, Ltd new | 66,830 | $2M | 0.1% | 2026-Q1 |
| Nuveen, LLC | 62,584 | $2M | 0.1% | 2026-Q1 |
| Caldwell Investment Management Ltd. | 60,800 | $2M | 0.1% | 2026-Q1 |
| INTACT INVESTMENT MANAGEMENT INC. trimmed | 53,389 | $2M | 0.1% | 2026-Q1 |
| GOLDMAN SACHS GROUP INC trimmed | 52,251 | $1M | 0.1% | 2026-Q1 |
| PCJ Investment Counsel Ltd. added | 50,000 | $1M | 0.0% | 2026-Q1 |
| GUARDIAN CAPITAL LP trimmed | 46,955 | $1M | 0.0% | 2026-Q1 |
| Aviso Financial Inc. trimmed | 45,760 | $1M | 0.0% | 2026-Q1 |
| BANK OF NOVA SCOTIA TRUST CO added | 34,332 | $968K | 0.0% | 2026-Q1 |
| VANGUARD GROUP INC trimmed | 2,339,481 | $64M | 2.3% | 2025-Q4 stale |
| Burgundy Asset Management Ltd. trimmed | 1,807,557 | $50M | 1.8% | 2025-Q3 stale |
| Capital World Investors | 1,196,000 | $38M | 1.3% | 2025-Q2 stale |
| HEALTHCARE OF ONTARIO PENSION PLAN TRUST FUND | 753,492 | $21M | 0.7% | 2025-Q4 stale |
| MOORE CAPITAL MANAGEMENT, LP trimmed | 611,120 | $19M | 0.7% | 2025-Q2 stale |
| NICOLA WEALTH MANAGEMENT LTD. added | 523,300 | $13M | 0.5% | 2025-Q1 stale |
| Galibier Capital Management Ltd. trimmed | 447,446 | $12M | 0.4% | 2025-Q3 stale |
| AGF MANAGEMENT LTD trimmed | 400,140 | $11M | 0.4% | 2025-Q4 stale |
| Foresight Group Ltd Liability Partnership added | 388,892 | $10M | 0.4% | 2025-Q3 stale |
| PICTON MAHONEY ASSET MANAGEMENT new | 279,805 | $9M | 0.3% | 2025-Q2 stale |
| JARISLOWSKY, FRASER Ltd trimmed | 334,904 | $9M | 0.3% | 2025-Q3 stale |
| Heathbridge Capital Management Ltd. trimmed | 323,300 | $8M | 0.3% | 2025-Q1 stale |
| Allspring Global Investments Holdings, LLC trimmed | 251,058 | $6M | 0.2% | 2025-Q1 stale |
| Select Equity Group, L.P. new | 242,640 | $6M | 0.2% | 2025-Q1 stale |
| Roubaix Capital, LLC added | 223,532 | $6M | 0.2% | 2025-Q3 stale |
| Polar Asset Management Partners Inc. added | 180,000 | $5M | 0.2% | 2025-Q4 stale |
| Lombard Odier Asset Management (Europe) Ltd added | 122,148 | $4M | 0.1% | 2025-Q2 stale |
| NATIXIS ADVISORS, LLC added | 98,912 | $3M | 0.1% | 2025-Q2 stale |
| UBS AM, A DISTINCT BUSINESS UNIT OF UBS ASSET MANAGEMENT AMERICAS LLC trimmed | 80,962 | $3M | 0.1% | 2025-Q2 stale |
| MILLENNIUM MANAGEMENT LLC added | 75,879 | $2M | 0.1% | 2025-Q4 stale |
| AYAL Capital Advisors Ltd new | 72,200 | $2M | 0.1% | 2025-Q4 stale |
| Fiera Capital Corp trimmed | 71,007 | $2M | 0.1% | 2025-Q4 stale |
| Bastion Asset Management Inc. new | 72,655 | $2M | 0.1% | 2025-Q3 stale |
| Ewing Morris & Co. Investment Partners Ltd. added | 31,600 | $1M | 0.0% | 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.