Mar 31, 2026 filings. Quarterly 13F reports arrive up to 45 days after quarter end; this register is filed through May 29, 2026.
212 institutional managers reported holding AMBP for the quarter ended Mar 31, 2026. Together they hold about 20% of shares outstanding; the top 10 hold 11%. 38 opened new positions; 29 closed out. Complete ranked register from SEC 13F filings.
| manager | shares | % out | value (Mar 31, 2026 close) | change | held since |
|---|---|---|---|---|---|
| Canyon Capital (focused) | 11.52M | 1.93% | $46.7M | trimmed -7.4% | 2021 Q3 |
| Arini Captial Management LTD (focused) | 11.25M | 1.88% | $45.5M | unchanged | 2025 Q4 |
| BlackRock | 7.73M | 1.29% | $31.3M | trimmed -3.5% | 2021 Q4 |
| Goldman Sachs | 7.29M | 1.22% | $29.5M | added +7.3% | 2021 Q3 |
| Platinum Equity Advisors, LLC/DE (focused) | 5.31M | 0.89% | $21.5M | unchanged | 2022 Q3 |
| Private Management Group INC | 5.02M | 0.84% | $20.3M | trimmed -1.3% | 2021 Q4 |
| Dimensional Fund Advisors | 4.64M | 0.78% | $18.8M | added +20.9% | 2021 Q4 |
| Weiss Asset Management LP | 4.52M | 0.76% | $18.3M | added +11276.2% | 2025 Q4 |
| Diameter Capital Partners LP (focused) | 4.47M | 0.75% | $18.1M | trimmed -16.9% | 2021 Q3 |
| Empyrean Capital Partners, LP | 4.00M | 0.67% | $16.2M | unchanged | 2021 Q3 |
| Arrowstreet Capital | 3.27M | 0.55% | $13.2M | added +28.4% | 2024 Q2 |
| Mirae Asset Global Etfs Holdings LTD. | 3.11M | 0.52% | $12.6M | trimmed -71.3% | 2024 Q3 |
| Monarch Alternative Capital LP (focused) | 2.96M | 0.49% | $12.0M | trimmed -44.8% | 2025 Q3 |
| Renaissance Technologies | 2.89M | 0.48% | $11.7M | added +31.9% | 2021 Q4 |
| State Street | 2.52M | 0.42% | $10.2M | added +0.5% | 2021 Q4 |
| Vanguard Group | 2.04M | 0.34% | $8.3M | added +2.3% | 2021 Q4 |
| Gilman Hill Asset Management, LLC | 1.99M | 0.33% | $8.1M | unchanged | 2022 Q2 |
| Jacobs Levy Equity Management, INC | 1.92M | 0.32% | $7.8M | trimmed -6.3% | 2024 Q1 |
| Geode Capital | 1.88M | 0.32% | $7.6M | added +2.4% | 2021 Q4 |
| Mountaineer Partners Management, LLC (focused) | 1.88M | 0.31% | $7.6M | added +27.8% | 2024 Q4 |
| Nuveen | 1.74M | 0.29% | $7.0M | unchanged | 2021 Q4 |
| Morgan Stanley | 1.74M | 0.29% | $7.0M | unchanged | 2021 Q3 |
| UBS | 1.49M | 0.25% | $6.0M | added +25.3% | 2021 Q4 |
| Gamco Investors, INC. et al | 1.42M | 0.24% | $5.8M | trimmed -2.1% | 2021 Q3 |
| Millennium Management | 1.36M | 0.23% | $5.5M | added +66.4% | 2021 Q3 |
| Northern Trust | 1.33M | 0.22% | $5.4M | added +3.2% | 2021 Q4 |
| Charles Schwab Investment Management | 1.26M | 0.21% | $5.1M | trimmed -15% | 2021 Q4 |
| GAMCO (Gabelli) | 886.5k | 0.15% | $3.6M | trimmed -2.2% | 2021 Q3 |
| Hillsdale Investment Management INC. | 869.1k | 0.14% | $3.5M | added +0.7% | 2025 Q2 |
| Two Sigma | 854.6k | 0.14% | $3.5M | added +140.6% | 2024 Q1 |
| Mackenzie Financial CORP | 839.9k | 0.14% | $3.4M | added +125% | 2024 Q2 |
| AQR Capital | 825.3k | 0.14% | $3.3M | added +5.1% | 2023 Q2 |
| HRT Financial LP | 797.8k | 0.13% | $3.2M | added +306.7% | 2022 Q1 |
| Royal Bank OF Canada | 698.4k | 0.12% | $2.8M | trimmed -6.7% | 2021 Q3 |
| Jane Street | 664.8k | 0.11% | $2.7M | opened | 2026 Q1 |
| Tudor Investment | 626.4k | 0.10% | $2.5M | trimmed -14.4% | 2025 Q2 |
| CWA Asset Management Group, LLC | 614.6k | 0.10% | $2.5M | added +22.9% | 2024 Q3 |
| Qube Research & Technologies LTD | 565.9k | 0.10% | $2.3M | opened | 2026 Q1 |
| Martingale Asset Management L P | 558.7k | 0.09% | $2.3M | added +197.1% | 2025 Q4 |
| BNY Mellon | 469.9k | 0.08% | $1.9M | trimmed -6.2% | 2021 Q4 |
| Janney Montgomery Scott LLC | 447.7k | 0.07% | $1.8M | trimmed -6.5% | 2022 Q2 |
| Contrarian Capital Management, L.l.c. (focused) | 413.7k | 0.07% | $1.7M | unchanged | 2022 Q4 |
| Citadel Advisors | 407.7k | 0.07% | $1.7M | trimmed -28.9% | 2021 Q3 |
| Invesco | 372.1k | 0.06% | $1.5M | trimmed -5.8% | 2021 Q4 |
| Healthcare OF Ontario Pension Plan Trust Fund | 353.0k | 0.06% | $1.4M | unchanged | 2021 Q3 |
| Citigroup INC | 350.6k | 0.06% | $1.4M | trimmed -0.9% | 2021 Q4 |
| ExodusPoint | 313.9k | 0.05% | $1.3M | opened | 2026 Q1 |
| Point72 | 305.7k | 0.05% | $1.2M | trimmed -30.9% | 2023 Q4 |
| Algert Global LLC | 297.3k | 0.05% | $1.2M | opened | 2025 Q3 |
| Ameriprise Financial INC | 292.7k | 0.05% | $1.2M | trimmed -19.5% | 2024 Q4 |
Largest 50 of 212 shown; the full ranked, searchable register is at boothcheck.com/holders/AMBP. Related filers are grouped using the filings' own included-manager declarations. Historically, several managers opening new positions in the same quarter said almost nothing about the quarter that followed (59,118 cases since 2013). A filed record, not a forecast. Nothing here is investment advice.