Earnings Per Share

Basic net income per share attributable to Vertex common shareholders is based upon the weighted-average number of common shares outstanding during the period, excluding restricted stock, restricted stock units and performance-based restricted stock units, or “PSUs,” that have been issued but are not yet vested. Diluted net income per share attributable to Vertex common shareholders is based upon the weighted-average number of common shares outstanding during the period plus additional weighted-average common equivalent shares outstanding during the period when the effect is dilutive.

The following table sets forth the computation of basic and diluted net income per share for the periods ended:



	Three Months Ended March 31,
	2019		2018
	(in thousands, except per share amounts)
Basic net income attributable to Vertex per common share calculation:
Net income attributable to Vertex common shareholders	$	268,631	$	210,263
Less: Undistributed earnings allocated to participating securities	—		(99		)
Net income attributable to Vertex common shareholders—basic	$	268,631	$	210,164

Basic weighted-average common shares outstanding	255,695		253,231
Basic net income attributable to Vertex per common share	$	1.05	$	0.83

Diluted net income attributable to Vertex per common share calculation:
Net income attributable to Vertex common shareholders	$	268,631	$	210,263
Less: Undistributed earnings allocated to participating securities	—		(97		)
Net income attributable to Vertex common shareholders—diluted	$	268,631	$	210,166

Weighted-average shares used to compute basic net income per common share	255,695		253,231
Effect of potentially dilutive securities:
Stock options	2,585		3,248
Restricted stock and restricted stock units (including PSUs)	1,870		2,013
Employee stock purchase program	25		34
Weighted-average shares used to compute diluted net income per common share	260,175		258,526
Diluted net income attributable to Vertex per common share	$	1.03	$	0.81

The Company did not include the securities in the following table in the computation of the net income per share attributable to Vertex common shareholders calculations because the effect would have been anti-dilutive during each period:



	Three Months Ended March 31,
	2019	2018
	(in thousands)
Stock options	2,837	1,633
Unvested restricted stock and restricted stock units (including PSUs)	6	4