Net Income (Loss) Per Common Share

Basic and diluted net income (loss) per common share is determined by dividing net income (loss) by the weighted average common shares and pre-funded warrants outstanding during the period. For the periods when there is a net loss, shares underlying stock options and RSUs have been excluded from the calculation of diluted net loss per common share because the effect of including such shares would be anti-dilutive. Therefore, the weighted average common shares used to calculate both basic and diluted net loss per common share would be the same.

The following table sets forth the computation of basic and diluted net income (loss) per common share for the periods indicated:



	Years ended December 31,
	2019			2018		2017
Basic and diluted net income (loss) per common share calculation:
Net income (loss)	$	(58,859	)	$	63,087	$	114,205
Weighted average common shares outstanding - basic	42,224			37,061		35,919
Plus: net effect of dilutive stock options and unvested restricted stock units	—			27		88
Weighted average common shares outstanding - dilutive	42,224			37,088		36,007
Net income (loss) per common share - basic	$	(1.39	)	$	1.70	$	3.18
Net income (loss) per common share - diluted	$	(1.39	)	$	1.70	$	3.17

The following potentially dilutive securities have been excluded from the computations of diluted weighted average common shares outstanding for the periods presented, as the effect of including such shares would be anti-dilutive:



	Years ended December 31,
	2019	2018	2017
Stock options outstanding	6,780	5,873	5,179
Restricted stock units	1,481	601	182
Total	8,261	6,474	5,361