The following table sets forth the computation of basic and diluted shares (in thousands):

	Years Ended December 31,
	2020		2019		2018
Denominator:
Weighted average common shares outstanding		82,840		49,120		48,823
Unvested common shares subject to repurchase		—		—		-
Total common shares-basic		82,840		49,120		48,823
Effect of dilutive securities:
Options		1		—		—
Restricted stock awards and units		1,015		—		—
Total common shares-diluted		83,856		49,120		48,823

Basic net income (loss) per share is computed using the weighted average number of shares of common stock outstanding during the period, excluding any unvested restricted stock awards that are subject to repurchase. Diluted net income (loss) per share is computed using the treasury stock method to calculate the weighted average number of shares of common stock and, if dilutive, potential common shares outstanding during the period. Potentially dilutive common shares include unvested restricted stock awards and units and incremental common shares issuable upon the exercise of stock options, less shares repurchased from assumed proceeds. The assumed proceeds calculation includes actual proceeds to be received from the employee upon exercise and the average unrecognized stock compensation cost during the period.

For the year ended December 31, 2020, 2.1 million shares subject to stock options and restricted stock awards and units were excluded from the computation of diluted net income per share as they were anti-dilutive.

For each of the years ended December 31, 2019 and 2018, there was no difference in the weighted average number of common shares used for the calculation of basic and diluted loss per share as the effect of all potentially dilutive shares outstanding was anti-dilutive. A total of 1.3 million and 2.9 million shares subject to stock options and restricted stock awards and units were excluded for the years ended December 31, 2019 and 2018, respectively, from the computation of diluted net loss per share because including them would have been anti-dilutive.