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Biggest moves on record

Every trading day we hold, as a bar. The five biggest are marked.

  1. 1+8.5%6 Feb 2026Low
  2. 2−8.2%14 Jul 2026Moderate
  3. 3+7.0%26 Jun 2026High
  4. 4−6.4%14 May 2026Low
  5. 5+6.0%29 Apr 2026Low

Every day, by size of move

265 trading days, 2025–2026. One square is one day.

  • Max00.0%
  • Very High00.0%
  • High10.4%
  • Moderate41.5%
  • Low5821.9%
  • Very Low20276.2%

Biggest moves on record

Every week we hold, as a bar. The five biggest are marked.

  1. 1+38.6%Week of7 Jun 2021Max
  2. 2+35.0%Week of26 Sep 2022Very High
  3. 3+16.4%Week of29 Sep 2025Low
  4. 4−12.4%Week of12 Jan 2026Very High
  5. 5+11.8%Week of2 Feb 2026Low

Every week, by size of move

302 weeks, 2021–2026. One square is one week.

  • Max10.3%
  • Very High20.7%
  • High00.0%
  • Moderate10.3%
  • Low4213.9%
  • Very Low25684.8%

Biggest moves on record

Every month we hold, as a bar. The five biggest are marked.

  1. 1+36.7%Sep 2022High
  2. 2+32.9%Apr 2011Moderate
  3. 3+29.5%Jun 2021Moderate
  4. 4+28.3%Oct 2019Very High
  5. 5−27.9%Mar 2019Very High

Every month, by size of move

252 months, 2005–2026. One square is one month.

  • Max00.0%
  • Very High20.8%
  • High20.8%
  • Moderate62.4%
  • Low7730.6%
  • Very Low16565.5%

Monthly performance

Over the past 22 years, BIIB rose most often in May (15 of 22) and fell most often in April (14 of 22).

How it reacted to its last results

ReportedResultOn the day
28 Oct 2026 Beat$2.62 vs $1.99 expected −3.4%
29 Jul 2026 Beat$3.60 vs $2.03 expected +1.8%
29 Apr 2026 Beat$3.57 vs $2.95 expected +6.0%
6 Feb 2026 Beat$1.99 vs $1.62 expected +8.5%

Beat or missed means profit per share came in above or below what experts expected. The price move is for the first trading day the results could move.

Compared with its neighbours

On a normal day, BIIB moves about 1.3% up or down. That is livelier than 6 in 10 shares we follow.

Industry · Health Care

LLYEli Lilly and Co.UNHUnitedHealth GroupJNJJohnson & JohnsonABBVAbbVie Inc.MRKMerck & Co.NVSNovartis AGAZNAstraZeneca plcNVONovo Nordisk A/S

and 47 more

In the news

Recent headlines about Biogen Inc., from the outlets that wrote them.

  1. 01Simply Wall St28 minutes agoBiogen (BIIB) Just Gave Investors Something To Think About
  2. 02MarketWatch21 hours agoBiogen Inc. stock outperforms competitors on strong trading day
  3. 03Investing.com Australia1 day agoFreedom Broker raises Biogen stock price target on strong results By Investing.com
  4. 04The Globe and Mail1 day agoBiogen (BIIB) Receives a Buy from TD Cowen
  5. 05Yahoo! Finance Canada1 day agoBiogen Inc. (BIIB) Stock Forecasts
  6. 06GuruFocus2 days agoBIIB Maintained by UBS -- Price Target Raised to $300