Basic earnings per share is computed by dividing net income (loss) attributable to common stockholders by the weighted-average number of common shares outstanding during the period without consideration for common stock equivalents. Diluted net income per share attributable to common stockholders is computed by dividing net income by the weighted-average number of common shares outstanding during the period and potentially dilutive common stock equivalents, including stock options and restricted stock units, except in cases where the effect of the common stock equivalent would be antidilutive. Potential common stock equivalents consist of common stock issuable upon exercise of stock options and vesting of restricted stock units using the treasury stock method. For periods of net loss, basic and diluted earnings per share are the same as the effect of the assumed exercise of stock options and vesting of restricted stock units is anti-dilutive.

The sale of 2,820,464 shares of the Company’s common stock to the Investor on April 25, 2018 resulted in an immediate increase in the outstanding shares used to calculate the weighted-average common shares outstanding for the year ended December 31, 2018 (see Note 13, Stockholders' Equity).

The following table presents the calculation of basic and diluted net income (loss) per share attributable to common stockholders for the years ended December 31, 2019, 2018 and 2017:

	Year Ended December 31,
	2019			2018		2017
	(in thousands, except per share data)
Basic earnings (loss) per share:
Net income (loss) attributable to common stockholders (numerator)	$	(18,566	)	$	78,481	$	98,983
Shares used in computation (denominator)
Weighted-average common shares outstanding		91,247			89,447		86,297
Basic earnings (loss) per share	$	(0.20	)	$	0.88	$	1.15
Diluted earnings (loss) per share:
Net income (loss) attributable to common stockholders (numerator)	$	(18,566	)	$	78,481	$	98,983
Shares used in computation (denominator)
Weighted-average common shares outstanding		91,247			89,447		86,297
Effect of dilutive securities:
Stock options		—			1,601		1,059
Restricted stock units		—			1,306		826
Weighted-average diluted shares		91,247			92,354		88,182
Diluted earnings (loss) per share	$	(0.20	)	$	0.85	$	1.12

The number of shares of common stock underlying stock-based awards excluded from the calculation of diluted net income (loss) per share attributable to common stockholders because their effect would have been antidilutive for the years ended December 31, 2019, 2018 and 2017 were as follows:

	Year Ended December 31,
	2019		2018		2017
	(in thousands)
Anti-dilutive shares underlying stock-based awards:
Stock options		2,750		216		—
Restricted stock units		3,096		223		36