Net Loss per Share

12 Months Ended

Dec. 31, 2015

4. Net Loss per Share

Basic and diluted net loss per share is calculated by dividing net loss by the weighted-average number of common shares outstanding for the period less weighted average shares subject to repurchase, of which there were none in 2015, 2014 or 2013. Outstanding stock options, warrants, and unvested restricted stock units are not included in the diluted net loss per share calculation for the fiscal years ended December 31, 2015, 2014 and 2013 as the inclusion of such shares would have had an anti-dilutive effect. Potentially anti-dilutive securities include the following (in thousands):

	Year Ended December 31,
	2015		2014		2013
Outstanding stock options		2,130		2,429		1,657
Unvested restricted stock units		58		371		315
Warrants to purchase common stock		5,763		6,561		6,462
Convertible debt		5,499		4,803		651