14. Net Loss per Share

Basic and diluted net loss per share attributable to common stockholders was calculated as follows (in thousands, except share and per share amounts):


	Year ended December 31,
	2019		2018		2017
Numerator:
Net Loss	$	(163,458)		(89,195)		(43,847)
Accretion of Series A redeemable convertible preferred stock to redemption value		—		—		(656)
Net loss attributable to common stockholders	$	(163,458)	$	(89,195)	$	(44,503)

Denominator:
Weighted average common shares outstanding, basic and diluted		78,688,878		39,285,468		8,023,785
Net loss per share, basic and diluted	$	(2.08)	$	(2.27)	$	(5.55)

Upon the issuance of Series A Preferred Stock, the holders of such shares were entitled to cumulative dividends of 8.0% per year, compounding annually. In connection with the issuance and sale of Series B Preferred Stock in June 2017, the holders of Series A Preferred Stock agreed to remove the cumulative dividend and redemption rights associated with the Series A Preferred Stock. Accordingly, during the year ended December 31, 2017, the calculation of net loss attributable to common stockholders included the accretion of Series A redeemable convertible preferred stock to redemption value.

The Company’s potential dilutive securities have been excluded from the computation of diluted net loss per share as the effect would be to reduce the net loss per share. Therefore, the weighted average number of common shares outstanding used to calculate both basic and diluted net loss per share attributable to common stockholders is the same. The Company excluded the following potential common shares from the periods in the table above, presented based on amounts outstanding at each period end, from the computation of diluted net loss per share attributable to common stockholders for the periods indicated because including them would have had an anti-dilutive effect:


	Year ended December 31,
	2019	2018	2017
Convertible preferred stock (as converted to common stock)	—	—	43,933,006
Warrants to purchase convertible preferred stock (as converted to common stock)	—	—	135,567
Restricted common stock (1)	376,514	2,230,235	6,277,014
Stock options to purchase common stock	15,103,907	14,784,770	4,661,635
	15,480,421	17,015,005	55,007,222

(1)

Includes unvested restricted stock and, in 2018 and 2017, vested restricted stock issued for promissory notes.