BIOGEN INC. (BIIB) - Dilution Analysis

Visualizing historical and potential share dilution over time

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Dilution Analysis

Low Risk

Limited dilution potential

Last updated: April 29, 2026

Risk Assessment Details

Potential Dilution: 0.0% of current shares

Recent Dilution: 1.09% (2 years)

Historical Dilution Factor: minimal recent dilution

Outstanding Shares

150M

Potential Supply

Additional shares possible

Splits

None

Past 2 years

Summary

BIIB currently has 147M outstanding shares. with minimal authorized share overhang for future dilution. The company has minimally diluted shareholders by 1.09% over the past 2 years.

Share Structure Timeline

Outstanding Shares

Total Supply

Historical Data Points

Date	Event	Outstanding
Apr 29, 2026	10-Q filing \| 147.2M shares outstanding	150M
Jul 31, 2025	10-Q filing \| 146.7M shares outstanding	150M
May 01, 2025	10-Q filing \| 146.6M shares outstanding	150M
Feb 12, 2025	10-K filing \| 145.9M shares outstanding	150M
Oct 30, 2024	10-Q filing \| 145.7M shares outstanding	150M
Aug 01, 2024	10-Q filing \| 145.6M shares outstanding	150M
Apr 24, 2024	10-Q filing \| 145.9M shares outstanding	150M
Feb 14, 2024	10-K filing \| 145.6M shares outstanding	150M
Nov 08, 2023	10-Q filing \| 144.8M shares outstanding	140M
Jul 25, 2023	10-Q filing \| 144.7M shares outstanding	140M
Apr 25, 2023	10-Q filing \| 144.4M shares outstanding	140M
Feb 15, 2023	10-K filing \| 145.3M shares outstanding	150M
Oct 25, 2022	10-Q filing \| 144.4M shares outstanding	140M
Jul 20, 2022	10-Q filing \| 145.9M shares outstanding	150M
May 03, 2022	10-Q filing \| 147.1M shares outstanding	150M
Feb 03, 2022	10-K filing \| 149.1M shares outstanding	150M
Oct 20, 2021	10-Q filing \| 148.0M shares outstanding	150M
Jul 22, 2021	10-Q filing \| 149.7M shares outstanding	150M
Apr 22, 2021	10-Q filing \| 151.9M shares outstanding	150M
Feb 03, 2021	10-K filing \| 160.9M shares outstanding	160M
Oct 21, 2020	10-Q filing \| 156.9M shares outstanding	160M
Jul 22, 2020	10-Q filing \| 160.6M shares outstanding	160M
Apr 23, 2020	10-Q filing \| 172.8M shares outstanding	170M
Feb 06, 2020	10-K filing \| 187.1M shares outstanding	190M

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