What if you'd held BIIB?
A $1,000 investment in Biogen Inc. (BIIB) at the month-end close of 1991-09 would be worth $70,899 at the close of 2026-08 — +6989.9% total return, dividends reinvested. The same $1,000 in the S&P 500 would be worth $19,873.
Your scenario
Result
If you'd bought $1,000 at the start of each year
Value of $1,000 invested on January 1 of each year, held to 2026-08, dividends included. Click any year for the full story.
Every year, $1,000 from 1991
| Year | Value of $1,000 | Year return |
|---|---|---|
| 1991 | $1,000 | — |
| 1992 | $673 | -32.7% |
| 1993 | $442 | -34.3% |
| 1994 | $163 | -63.0% |
| 1995 | $1,500 | +818.1% |
| 1996 | $1,826 | +21.8% |
| 1997 | $2,644 | +44.7% |
| 1998 | $3,615 | +36.7% |
| 1999 | $15,113 | +318.1% |
| 2000 | $29,159 | +92.9% |
| 2001 | $31,809 | +9.1% |
| 2002 | $15,307 | -51.9% |
| 2003 | $16,936 | +10.6% |
| 2004 | $30,738 | +81.5% |
| 2005 | $20,895 | -32.0% |
| 2006 | $22,700 | +8.6% |
| 2007 | $26,267 | +15.7% |
| 2008 | $21,980 | -16.3% |
| 2009 | $24,689 | +12.3% |
| 2010 | $30,941 | +25.3% |
| 2011 | $50,784 | +64.1% |
| 2012 | $67,545 | +33.0% |
| 2013 | $129,012 | +91.0% |
| 2014 | $156,645 | +21.4% |
| 2015 | $141,371 | -9.8% |
| 2016 | $130,863 | -7.4% |
| 2017 | $147,010 | +12.3% |
| 2018 | $138,865 | -5.5% |
| 2019 | $136,931 | -1.4% |
| 2020 | $112,995 | -17.5% |
| 2021 | $110,715 | -2.0% |
| 2022 | $127,790 | +15.4% |
| 2023 | $119,414 | -6.6% |
| 2024 | $70,568 | -40.9% |
| 2025 | $81,214 | +15.1% |
| 2026 | $102,243 | +25.9% |
Best and worst month-end to buy
The best single month-end close to have bought BIIB was 1994-12 ($0.35): $1,000 then is $625,876 today. The worst was 2015-03 ($422): $1,000 then is $525.
FAQ
What would $1,000 in BIIB be worth today?
A $1,000 investment in Biogen Inc. (BIIB) at the start of 1991 would be worth about $70,899 today, a total return of +6989.9%. Dividends are reinvested in these figures.
What were the best and worst years for BIIB?
Biogen Inc. (BIIB)'s strongest calendar year since 1991 was 1995, a +818.1% return — $1,000 held through that year became about $9,181 by year-end. Its weakest year was 1994, at -63.0%.
Does the calculator include dividends and splits?
Yes where available. Prices are adjusted for both stock splits and reinvested dividends (total return), the same measure brokerages use.
How much would $100 per month in BIIB have grown?
Investing $100 at the end of every month since 1991-09 would have grown to about $1.61M on $42,000 invested.
Did BIIB beat the S&P 500?
Over the same period, $1,000 in the S&P 500 index would be worth $19,873. BIIB beat the S&P 500 by +256.8% in total return.
Is this investment advice?
No. Wall Street Regrets is an entertainment and education tool. Every number is a historical calculation, not a prediction, and past performance never guarantees future results.
Methodology
Biogen Inc. (BIIB) historical total-return data from 1991-09 to 2026-08, reduced to month-end closes for the tables above.
Returns use adjusted close prices from Yahoo Finance historical data — adjusted for stock splits and reinvested dividends — the same convention used by major brokerages. A "year" scenario invests $1,000 at the prior December's month-end close and values it at the latest available month-end close. Non-USD amounts are converted at historical month-end exchange rates (Yahoo Finance): to USD on the buy date and back to your currency at the latest rate, so the return reflects the currency move as well as the asset.
Month-end resolution means intra-month extremes are not captured in tables; the calculator uses exact trading-day closes where daily data is available. Figures ignore taxes, fees, and the currency effects of non-USD listings. History is not a forecast. Wall Street Regrets is entertainment, not investment advice.
What if you'd held…
Data: adjusted close prices via Yahoo Finance. As of 2026-08. Not financial advice.