How much did BIIB move each index today?
S&P 500: BIIB moved +3.33% and contributed +0.1 points of the index's +46.2-point move (0% of it), ranking #102 of 491 members by contribution to the move.
XBI: BIIB moved +3.33% and contributed +0.08 points of the index's +4.46-point move (2% of it), ranking #18 of 154 members by contribution to the move.
XLV: BIIB moved +3.33% and contributed +0.03 points of the index's +2.66-point move (1% of it), ranking #19 of 59 members by contribution to the move.
BIIB closed the 2026-10-09 session at 225.71; that day's move sits in the 94th percentile of its own past year. The stock is 1.3% below its 52-week closing high and +28.3% for the year so far.
BIIB in the S&P 500 beyond today
| window | BIIB return | points contributed | index move | rank |
|---|---|---|---|---|
| 1 week | +2.65% | +0.1 pts | +88.8 pts | #194 of 503 |
| 1 month | +4.77% | +0.2 pts | +219.8 pts | #130 of 503 |
| quarter to date | −0.08% | +0.0 pts | +160.0 pts | #348 of 503 |
| year to date | +28.25% | +0.6 pts | +966.0 pts | #156 of 503 |
Who moved with and against BIIB today?
On BIIB's side of the S&P 500 tape: MSFT (+11.3 pts), AMZN (+10.0 pts), PLTR (+2.8 pts). Pulling the other way: AAPL (−7.0 pts), NVDA (−3.7 pts), VZ (−2.7 pts).
Every member's contribution, top to bottom, is on the index dashboards; the day's story is in the market-close note. Machine-readable figures for this stock: /api/stock/BIIB, free to cite with attribution.