Earnings Per Share

Basic net income (loss) 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, which have been issued but are not yet vested. Diluted net income (loss) 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 (loss) per share for three years ended December 31, 2018:



	2018			2017			2016
	(in thousands, except per share amounts)
Basic net income (loss) attributable to Vertex per common share calculation:
Net income (loss) attributable to Vertex common shareholders	$	2,096,896		$	263,484		$	(112,052	)
Less: Undistributed earnings allocated to participating securities	(501		)	(293		)	—
Net income (loss) attributable to Vertex common shareholders—basic	$	2,096,395		$	263,191		$	(112,052	)

Basic weighted-average common shares outstanding	254,292			248,858			244,685
Basic net income (loss) attributable to Vertex per common share	$	8.24		$	1.06		$	(0.46	)

Diluted net income (loss) attributable to Vertex per common share calculation:
Net income (loss) attributable to Vertex common shareholders	$	2,096,896		$	263,484		$	(112,052	)
Less: Undistributed earnings allocated to participating securities	(492		)	(288		)	—
Net income (loss) attributable to Vertex common shareholders—diluted	$	2,096,404		$	263,196		$	(112,052	)

Weighted-average shares used to compute basic net income (loss) per common share	254,292			248,858			244,685
Effect of potentially dilutive securities:
Stock options	2,913			2,797			—
Restricted stock and restricted stock units (including PSUs)	1,963			1,542			—
Employee stock purchase plan	17			28			—
Weighted-average shares used to compute diluted net income (loss) per common share	259,185			253,225			244,685
Diluted net income (loss) attributable to Vertex per common share	$	8.09		$	1.04		$	(0.46	)

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



	2018	2017	2016
	(in thousands)
Stock options	2,217	3,554	12,642
Unvested restricted stock and restricted stock units (including PSUs)	5	411	3,546