Biogen (BIIB)
S&P 500 · Health Care · data since 1991-09-17 · last close 2026-09-09
Biogen (BIIB) monthly returns (%)
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2026 | 2.2 | 6.6 | -4.4 | 3.3 | 3.5 | 10.2 | -6.1 | 6.8 | -2.7 | · | · | · |
| 2025 | -5.9 | -2.4 | -2.6 | -11.5 | 7.2 | -3.2 | 1.9 | 3.3 | 5.9 | 10.1 | 18.0 | -3.4 |
| 2024 | -4.7 | -12.0 | -0.6 | -0.4 | 4.7 | 3.1 | -8.0 | -4.0 | -5.3 | -10.2 | -7.7 | -4.8 |
| 2023 | 5.0 | -7.2 | 3.0 | 9.4 | -2.6 | -3.9 | -5.2 | -1.1 | -3.9 | -7.6 | -1.5 | 10.6 |
| 2022 | -5.8 | -6.6 | -0.2 | -1.5 | -3.6 | 2.0 | 5.5 | -9.2 | 36.7 | 6.2 | 7.7 | -9.3 |
| 2021 | 15.4 | -3.4 | 2.5 | -4.4 | 0.1 | 29.5 | -5.6 | 3.7 | -16.5 | -5.8 | -11.6 | 1.8 |
| 2020 | -9.4 | 14.7 | 2.6 | -6.2 | 3.5 | -12.9 | 2.7 | 4.7 | -1.4 | -11.1 | -4.7 | 1.9 |
| 2019 | 10.9 | -1.7 | -27.9 | -3.0 | -4.3 | 6.7 | 1.7 | -7.6 | 6.0 | 28.3 | 0.4 | -1.0 |
| 2018 | 9.2 | -16.9 | -5.3 | -0.1 | 7.4 | -1.3 | 15.2 | 5.7 | -0.1 | -13.9 | 9.7 | -9.8 |
| 2017 | -2.2 | 4.1 | -5.3 | -0.8 | -8.6 | 9.5 | 6.7 | 9.3 | -1.1 | -0.5 | 3.4 | -1.1 |
| 2016 | -10.9 | -5.0 | 0.3 | 5.6 | 5.4 | -16.5 | 19.9 | 5.4 | 2.4 | -10.5 | 5.0 | -3.6 |
| 2015 | 14.6 | 5.3 | 3.1 | -11.4 | 6.2 | 1.8 | -21.1 | -6.7 | -1.9 | -0.5 | -1.3 | 6.8 |
| 2014 | 11.8 | 9.0 | -10.2 | -6.1 | 11.2 | -1.3 | 6.0 | 2.6 | -3.6 | -2.9 | -4.2 | 10.3 |
| 2013 | 6.6 | 6.6 | 15.8 | 13.7 | 8.5 | -9.4 | 1.4 | -2.3 | 13.0 | 1.4 | 19.2 | -3.9 |
| 2012 | 7.2 | -1.3 | 8.2 | 6.4 | -2.4 | 10.4 | 1.0 | 0.5 | 1.8 | -7.4 | 7.9 | -1.8 |
| 2011 | -2.4 | 4.5 | 7.4 | 32.9 | -3.0 | 12.9 | -4.7 | -7.5 | -1.1 | 24.9 | -1.2 | -4.3 |
| 2010 | 0.5 | 2.4 | 4.3 | -7.1 | -11.0 | 0.0 | 17.8 | -3.7 | 4.3 | 11.7 | 2.0 | 4.8 |
| 2009 | 2.1 | -5.4 | 13.9 | -7.8 | 7.1 | -12.8 | 5.3 | 5.6 | 0.6 | -16.6 | 11.4 | 14.0 |
| 2008 | 7.1 | -4.3 | 5.7 | -1.6 | 3.4 | -10.9 | 24.8 | -27.0 | -1.3 | -15.4 | -0.6 | 12.6 |
| 2007 | -1.7 | -6.5 | -1.8 | 6.4 | 10.6 | 2.5 | 5.7 | 12.9 | 3.9 | 12.2 | -0.4 | -23.2 |
| 2006 | -1.2 | 5.6 | -0.3 | -4.8 | 4.0 | -0.7 | -9.2 | 5.1 | 1.1 | 6.5 | 9.8 | -5.9 |
| 2005 | -2.5 | -40.5 | -10.7 | 5.0 | 7.9 | -11.9 | 14.1 | 7.3 | -6.3 | 2.9 | 5.4 | 5.8 |
| 2004 | 17.1 | 29.0 | 0.3 | 6.1 | 5.3 | 1.8 | -5.1 | -1.1 | 3.1 | -4.9 | 0.9 | 13.5 |
| 2003 | -3.3 | -10.4 | 19.0 | -4.3 | 16.7 | -11.2 | -0.6 | 2.8 | -4.1 | 5.6 | 8.7 | -3.9 |
| 2002 | -13.7 | 5.7 | 2.4 | -14.5 | -21.9 | -17.4 | 25.8 | -9.9 | 3.3 | 10.8 | -28.7 | 1.1 |
| 2001 | -6.9 | -4.1 | -29.1 | 23.0 | 25.2 | 9.9 | -20.3 | 9.8 | -16.4 | 21.0 | 17.2 | -1.9 |
| 2000 | 28.4 | 11.6 | -30.3 | -34.9 | -0.3 | 83.8 | 4.7 | 13.7 | 25.6 | 11.8 | -11.3 | 8.9 |
| 1999 | 7.5 | -14.2 | 18.6 | -1.2 | -0.6 | 52.8 | 28.6 | 28.2 | -26.0 | 23.6 | 9.1 | 55.0 |
| 1998 | 21.4 | 8.7 | -2.5 | -18.6 | -12.5 | -25.2 | 0.5 | -24.0 | 31.9 | 25.8 | 12.6 | 39.8 |
| 1997 | -2.1 | 7.0 | -4.3 | -25.5 | 26.8 | 7.8 | 12.4 | 11.5 | 37.9 | -9.0 | -8.4 | -1.6 |
| 1996 | 10.3 | -5.8 | 9.9 | 29.8 | -10.8 | -10.2 | -33.0 | 50.8 | 2.7 | -9.9 | 12.1 | -2.1 |
| 1995 | 20.6 | 46.3 | 0.0 | 6.7 | 12.5 | 25.0 | 20.0 | 1.9 | 14.6 | 50.8 | 15.8 | 41.8 |
| 1994 | 13.0 | -19.2 | -26.2 | -6.5 | 3.5 | -35.0 | 12.8 | 0.0 | -13.6 | 21.1 | -13.0 | -15.0 |
| 1993 | -20.0 | 0.0 | -17.9 | -17.4 | 18.4 | -2.2 | -31.8 | 40.0 | -4.8 | 12.5 | 6.7 | -4.2 |
| 1992 | 19.2 | -9.7 | -21.4 | -27.3 | 0.0 | -17.2 | 28.3 | -16.2 | -8.8 | 46.1 | 10.5 | -16.7 |
| 1991 | · | · | · | · | · | · | · | · | 0.0 | -1.3 | -35.1 | 8.3 |
| Avg | 3.9 | -0.3 | -2.4 | -2.0 | 3.4 | 1.9 | 3.2 | 3.2 | 2.1 | 5.9 | 1.8 | 3.4 |
Values in %. Current and first-listed months are partial (greyed).
returnsview.com
BIIB seasonality — average by calendar month
Biogen has monthly history back to 1991. Its strongest month by median is May — positive in 22 of 35 years, median +3.5%, and higher in 6 of the last 9. February is the soft spot, down in 20 of 35 with a median of -1.7%. Across its full record it has closed 52% of months higher, swings ±14.6% in an average month and has fallen 90% peak to trough.
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg | +3.9% | -0.3% | -2.4% | -2.0% | +3.4% | +1.9% | +3.2% | +3.2% | +2.3% | +5.9% | +1.8% | +3.4% |
| Win rate | 57%/35 | 43%/35 | 46%/35 | 34%/35 | 63%/35 | 49%/35 | 66%/35 | 60%/35 | 49%/35 | 54%/35 | 60%/35 | 46%/35 |
Win rate = share of positive months / sample size.
BIIB risk & extremes
BIIB drawdown & rolling returns
Percent below the all-time high at each month-end — how far underwater the asset was.
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Frequently asked questions
What was Biogen's best month?+
Biogen's strongest completed month on record is June 2000, at +83.84%.
What was Biogen's worst month?+
Its weakest completed month on record is February 2005, at -40.50%.
Is Biogen up this year?+
Biogen is up 19.74% year to date, measured from its last close before 1 January.
What is Biogen's 1-year return?+
+46.75% over the past twelve months, comparing the latest close with the most recent close on or before the same date a year earlier.
What is Biogen's biggest drawdown?+
The deepest peak-to-trough fall on record is 90.0%, measured on month-end closes since 1991.
Which calendar month is historically best for Biogen?+
October has the highest average return across every completed October since 1991. An average is not a forecast.
About Biogen
Biogen is an S&P 500 company, a health care business worth about $31 billion. It turns lab coats into cash flows — with price receipts on this site going back to 1991. And the long game: $100 at its first close here (1991) would be about $6,929 today.
Did you know?
- Its best month on record was June 2000 at +83.84%; its worst, February 2005 at -40.5%.
Trivia for entertainment — the numbers come from our price data; the jokes don't.