Mar 31, 2026 filings. Quarterly 13F reports arrive up to 45 days after quarter end; this register is filed through May 29, 2026.
233 institutional managers reported holding AMSC for the quarter ended Mar 31, 2026. Together they hold about 74% of shares outstanding; the top 10 hold 37%. 48 opened new positions; 51 closed out. Complete ranked register from SEC 13F filings.
| manager | shares | % out | value (Mar 31, 2026 close) | change | held since |
|---|---|---|---|---|---|
| Vanguard Group | 4.14M | 9.21% | $139.8M | added +17.3% | ≤2013 |
| BlackRock | 3.98M | 8.86% | $134.6M | added +6.2% | ≤2013 |
| Baillie Gifford | 1.45M | 3.22% | $48.9M | trimmed -3.9% | 2020 Q3 |
| State Street | 1.26M | 2.81% | $42.6M | added +5.8% | 2019 Q2 |
| Geode Capital | 1.17M | 2.60% | $39.5M | added +7.2% | ≤2013 |
| Barrow Hanley Mewhinney & Strauss LLC | 1.14M | 2.54% | $38.5M | opened | 2026 Q1 |
| Nuveen | 1.02M | 2.27% | $34.5M | added +6.2% | 2024 Q2 |
| Oberweis Asset Management INC/ | 849.9k | 1.89% | $28.7M | added +1.7% | 2023 Q4 |
| AWM Investment Company, INC. | 801.6k | 1.78% | $27.1M | added +6.3% | 2015 Q2 |
| First Trust Advisors LP | 778.3k | 1.73% | $26.3M | added +14% | 2018 Q1 |
| Emerald Advisers, LLC | 757.4k | 1.69% | $25.6M | unchanged | 2024 Q4 |
| Goldman Sachs | 709.5k | 1.58% | $24.0M | trimmed -9.3% | 2017 Q2 |
| UBS | 688.2k | 1.53% | $23.3M | trimmed -16.3% | ≤2013 |
| Dimensional Fund Advisors | 658.3k | 1.47% | $22.3M | added +21.8% | ≤2013 |
| Morgan Stanley | 633.8k | 1.41% | $21.4M | trimmed -10.1% | ≤2013 |
| Telemark Asset Management, LLC | 600.0k | 1.33% | $20.3M | trimmed -3.2% | 2024 Q1 |
| D. E. Shaw | 567.6k | 1.26% | $19.2M | added +28.1% | 2017 Q2 |
| Royce & Associates | 542.8k | 1.21% | $18.3M | added +40.2% | 2017 Q1 |
| Legal & General Group PLC | 530.1k | 1.18% | $17.9M | added +90.7% | 2024 Q2 |
| Algert Global LLC | 490.0k | 1.09% | $16.6M | added +6.3% | 2024 Q4 |
| Arrowstreet Capital | 446.8k | 0.99% | $15.1M | trimmed -34.6% | 2024 Q1 |
| Emerald Mutual Fund Advisers Trust | 438.9k | 0.98% | $14.8M | added +0.8% | 2024 Q4 |
| BNP Paribas Financial Markets | 437.6k | 0.97% | $14.8M | added +425.9% | 2024 Q2 |
| Hood River Capital Management LLC | 398.7k | 0.89% | $13.5M | opened | 2026 Q1 |
| Northern Trust | 393.2k | 0.88% | $13.3M | added +9% | ≤2013 |
| Charles Schwab Investment Management | 385.4k | 0.86% | $13.0M | trimmed -0.5% | 2023 Q1 |
| Nomura Asset Management International INC. | 379.5k | 0.84% | $12.8M | trimmed -17.5% | 2025 Q4 |
| Qube Research & Technologies LTD | 329.4k | 0.73% | $11.1M | trimmed -45% | 2022 Q2 |
| Stephens Investment Management Group LLC | 308.5k | 0.69% | $10.4M | added +77.1% | 2025 Q3 |
| Portolan Capital Management, LLC | 295.6k | 0.66% | $10.0M | opened | 2026 Q1 |
| Panagora Asset Management INC | 256.4k | 0.57% | $8.7M | added +0.6% | 2024 Q3 |
| Invesco | 240.8k | 0.54% | $8.1M | trimmed -37.6% | 2016 Q2 |
| Essex Investment Management CO LLC | 227.6k | 0.51% | $7.7M | added +5.8% | 2023 Q3 |
| SEI Investments CO | 224.4k | 0.50% | $7.6M | added +184.8% | 2024 Q2 |
| Citadel Advisors | 216.7k | 0.48% | $7.3M | trimmed -35.8% | 2016 Q4 |
| Bank OF America CORP /DE/ | 209.5k | 0.47% | $7.1M | added +26.5% | 2018 Q1 |
| AQR Capital | 184.8k | 0.41% | $6.2M | added +26.6% | 2024 Q3 |
| Two Sigma | 169.0k | 0.38% | $5.7M | trimmed -47.4% | 2023 Q2 |
| Baird Financial Group, INC. | 163.3k | 0.36% | $5.5M | added +21% | 2024 Q4 |
| Palisades Investment Partners, LLC | 152.6k | 0.34% | $5.2M | added +5.8% | 2024 Q2 |
| Allspring Global Investments Holdings, LLC | 149.6k | 0.33% | $5.1M | trimmed -26.9% | 2024 Q3 |
| FMR (Fidelity) | 147.3k | 0.33% | $5.0M | added +18.4% | 2022 Q1 |
| Balyasny Asset Management | 144.1k | 0.32% | $4.9M | trimmed -5.7% | 2024 Q4 |
| ArrowMark Colorado Holdings LLC | 135.4k | 0.30% | $4.6M | added +22.6% | 2020 Q3 |
| BNY Mellon | 134.8k | 0.30% | $4.6M | trimmed -1.6% | 2017 Q4 |
| Raymond James Financial INC | 124.0k | 0.28% | $4.2M | trimmed -12.6% | 2021 Q4 |
| GMT Capital CORP | 108.1k | 0.24% | $3.7M | opened | 2018 Q2 |
| Millennium Management | 101.6k | 0.23% | $3.4M | added +30.1% | 2020 Q4 |
| Axiom Investors LLC /DE | 100.8k | 0.22% | $3.4M | trimmed -24.8% | 2025 Q3 |
| Swiss National Bank | 89.1k | 0.20% | $3.0M | unchanged | 2024 Q3 |
Largest 50 of 233 shown; the full ranked, searchable register is at boothcheck.com/holders/AMSC. 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.