IPO date
September 17, 1991
Total splits
2
Cumulative multiple
6
Split likelihood
Watch
Stock splits history for Biogen (BIIB) from 1999 to 2001
Cumulative multiple is the running product of split factors from the oldest row through each date.
| Type | Ratio | Pre-split | Post-split | |||
|---|---|---|---|---|---|---|
| January 18, 2001 | Stock split | 3:1 | x3 | x6 | $163.31 | $55.38 |
| December 21, 1999 | Stock split | 2:1 | x2 | x2 | $126.50 | $62 |
- January 18, 2001x6
- December 21, 1999x2
Pre-split price is the final regular-session close on a trading day strictly before the split calendar date. Post-split price is the first session open on or after that date. Both values come from unadjusted end-of-day bars for the company's primary listing.
The Type column reflects the data feed's event category (for example stock split vs stock dividend). When the feed labels a generic split but the ratio is reverse (e.g. 1:10), we show reverse stock split. Optional editorial context for a row appears next to the split ratio as an info icon (hover or keyboard focus on desktop; tap on mobile). The same text is listed under Row notes when that block is expanded.
Wondering why some rows show ratios like 51:50 or 2000:1973? Read: stock split ratios explained → How the cumulative column is computed: cumulative split multiplier explained. For ratios driven by spin-offs, see spin-offs explained. Or read the methodology for how prices and cumulative multiples are computed.
Split likelihood score for Biogen (BIIB)
Computed through June 13, 2026.
| Factor | Detail | Contribution |
|---|---|---|
| Absolute price | Price $200.05 → 36% of the price band | +14 |
| Personal split threshold | Price is 128% of the company's typical pre-split price ($155.95) | +28 |
| Split track record | 2 prior splits on record | +12 |
| Proximity to 52-week high | Price is 97% of the 52-week high | +12 |
| Timing | Last split over 20 years ago | ×0.70 |
An educational, rule-based score — not a prediction of any split and not investment advice. Splits are at the sole discretion of a company's board. How it's calculated · Will a stock split?
Stock splits — Healthcare
Healthcare peers of Biogen Inc. (BIIB), sorted by number of splits.
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