Earnings per Share (Tables)

9 Months Ended

Sep. 30, 2022

Earnings Per Share [Abstract]

Basic and diluted earnings per share

Basic and diluted shares outstanding used in our earnings per share calculation are calculated as follows:

	For the Three Months Ended September 30,				For the Nine Months Ended September 30,
(In millions)	2022		2021		2022		2021
Numerator:
Net income attributable to Biogen Inc.	$	1,134.7	$	329.2	$	2,496.5	$	1,187.9
Denominator:
Weighted average number of common shares outstanding	144.4		148.0		145.8		149.9
Effect of dilutive securities:
Time-vested restricted stock units	0.3		0.4		0.3		0.2
Market stock units	—		0.1		—		0.1
Performance stock units settled in stock	0.1		0.1		0.1		0.1
Dilutive potential common shares	0.4		0.6		0.4		0.4
Shares used in calculating diluted earnings per share	144.8		148.6		146.2		150.3