Income (Loss) Per Share

12 Months Ended

Dec. 31, 2020

Income (Loss) Per Share Basic income (loss) per share is computed by dividing net income (loss) attributable to common stockholders by the sum of the weighted-average number of common shares outstanding and the weighted-average number of shares issuable under the common stock warrants, representing 61 thousand shares during the year ended December 31, 2020 and 354 thousand shares during each of the years ended December 31, 2019 and 2018. The common stock warrants are included in the calculation of basic income (loss) per share because they were issuable for minimal consideration. As of March 31, 2020, the previously outstanding common stock warrants had been exercised for common stock and no warrants were outstanding.

The following table sets forth the computation of basic and diluted income (loss) per share (in thousands, except per share amounts):


	Year Ended December 31,
	2020		2019		2018
Net income (loss)	$	(409,086)	$	40,809	$	39,427
Less: Undistributed income allocated to participating securities (1)	—		438		556
Net income (loss) attributable to common stockholders	(409,086)		40,371		38,871
Plus: Net income effect of convertible securities	—		—		—
Numerator for diluted income (loss) per common share	$	(409,086)	$	40,371	$	38,871

Basic weighted-average common stock shares outstanding	53,295		50,352		45,726
Plus: dilutive effects of common stock equivalents (2)	—		118		29
Diluted weighted-average common stock shares outstanding	53,295		50,470		45,755

Basic income (loss) per common share	$	(7.68)	$	0.80	$	0.85
Diluted income (loss) per common share	$	(7.68)	$	0.80	$	0.85

Diluted income (loss) per common share excludes the following equity instruments because their effect would be anti-dilutive:
Shares of unvested restricted stock	475		182		68
Shares of stock options	2,229		1,577		1,304
Common stock equivalents using the if-converted method of settling the 5.00% Convertible Senior Notes	2,704		5,122		6,389

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(1)Participating securities include restricted stock that has been issued but had not yet vested. These participating securities were fully vested as of December 31, 2019.

(2)Entities with a net loss from continuing operations are prohibited from including potential common shares in the computation of diluted per share amounts. We have utilized the basic shares outstanding to calculate both basic and diluted loss per common share for the year ended December 31, 2020.