BIIB
Biogen Inc. · Healthcare · Drug Manufacturers - General
Momentum inputs (comparable managers):
holder breadth +12.5% ·
share flow +0.5% ·
net new positions +11.1%
· formula
Broad accumulation: rising shares across more holders
All ownership figures: tracked 13F managers only, common-stock positions, reporting period Q1 2025
| Quarter | Holders | Δ | Shares | Reported value | New | Exits |
|---|---|---|---|---|---|---|
| Q3 2026 | 3 | -1 | 75.75K | $11.04M | n/a | −3 |
| Q2 2026 | 159 | 0 | 117.81M | $25.44B | +6 | −7 |
| Q1 2026 | 163 | -1 | 110.78M | $20.30B | +4 | −6 |
| Q4 2025 | 163 | 0 | 123.15M | $21.67B | +2 | −1 |
| Q3 2025 | 24 | +1 | 81.72M | $11.44B | +1 | −1 |
| Q2 2025 | 21 | 0 | 78.50M | $9.86B | n/a | n/a |
| Q1 2025 | 18 | +2 | 41.87M | $5.73B | +3 | −1 |
| Q4 2024 | 16 | -1 | 41.64M | $6.37B | n/a | −1 |
| Q3 2024 | 16 | +2 | 32.39M | $6.28B | +2 | n/a |
| Q2 2024 | 14 | n/a | 30.72M | $7.12B | n/a | n/a |
| # | Manager | Shares | Δ shares | Value | Their weight | Held | ||
|---|---|---|---|---|---|---|---|---|
| 1 | PRIMECAP Management ✦ | 15.94M | -0.6% | $2.18B | 1.8% | ▼ Trim | 4 | SEC ↗ |
| 2 | State Street Global Advisors ✦ (passive) | 7.40M | 0.0% | $1.01B | 0.0% | ▼ Trim | 2 | SEC ↗ |
| 3 | Wellington Management ✦ | 4.67M | -5.2% | $639.38M | 0.1% | ▼ Trim | 4 | SEC ↗ ×5 |
| 4 | D. E. Shaw & Co. ✦ | 1.59M | -1.5% | $216.97M | 0.3% | ▼ Trim | 4 | SEC ↗ ×2 |
| 5 | AQR Capital Management ✦ | 1.37M | +153.6% | $187.26M | 0.2% | ▲ Add | 4 | SEC ↗ ×7 |
| 6 | T. Rowe Price ✦ | 1.15M | -40.5% | $157.53M | 0.0% | ▼ Trim | 4 | SEC ↗ ×2 |
| 7 | Renaissance Technologies ✦ | 804.51K | -32.5% | $110.09M | 0.2% | ▼ Trim | 4 | SEC ↗ |
| 8 | Fisher Asset Management ✦ | 299.03K | +65.3% | $40.92M | 0.0% | ▲ Add | 4 | SEC ↗ |
| 9 | Arrowstreet Capital ✦ | 214.78K | New | $29.39M | 0.0% | New | 1 | SEC ↗ |
| 10 | Adage Capital Partners ✦ | 70.77K | New | $9.68M | 0.0% | New | 1 | SEC ↗ |
“Their weight” = the position's share of that manager's reported 13F equity value: the conviction measure. ✦ = curated manager.
New buyers
| Arrowstreet Capital | $29.39M | 0.0% |
| Adage Capital Partners | $9.68M | 0.0% |
Exited
| No tracked exits this quarter. |
Full-market context: across ALL 13F filers (SEC structured data, Q1 2026): 995 holders, 132.27M shares, $23.30B reported. This is a different, older period than the tracked-universe figures above and the two are never mixed.
What else this security's tracked holders most often hold: shared-ownership counts, not fundamental relationships.