Earnings per Share

3 Months Ended

Mar. 31, 2016

Basic and diluted earnings per share are calculated as follows:



	For the Three Months Ended March 31,
(In millions)	2016		2015
Numerator:
Net income attributable to Biogen Inc.	$	970.9	$	822.5
Denominator:
Weighted average number of common shares outstanding	218.9		235.0
Effect of dilutive securities:
Stock options and employee stock purchase plan	0.1		0.1
Time-vested restricted stock units	0.2		0.3
Market stock units	0.1		0.2
Dilutive potential common shares	0.4		0.6
Shares used in calculating diluted earnings per share	219.3		235.6

Amounts excluded from the calculation of net income per diluted share because their effects were anti-dilutive were insignificant.