Basic net income per share is calculated by dividing net income by the weighted average number of common shares outstanding for the period. Diluted earnings per share is computed by dividing net income by the weighted average number of shares assuming dilution. Dilutive common shares outstanding is computed using the Treasury Stock Method and reflects the additional shares that would be outstanding if dilutive stock options were exercised and restricted stock units were settled for common shares during the period.

The weighted average number of common shares used to compute basic and diluted net income per share for the years ended December 31, 2020, 2019 and 2018 were as follows:

	For the Year Ended December 31,
	2020		2019		2018
Basic common shares outstanding		69,414		70,088		69,598
Common stock equivalents		1,851		1,997		1,884
Diluted common shares outstanding		71,265		72,085		71,482

For the years ended December 31, 2020, 2019 and 2018, certain unexercised stock options awards are excluded from our computation of diluted earnings per share, as these shares were out-of-the-money and their effect would have been anti-dilutive. The anti-dilutive options that were excluded from our computation of diluted earnings per share were 0.5 million, 0.7 million and 0.8 million shares for the years ended December 31, 2020, 2019 and 2018, respectively.

In addition to the common stock issued upon the exercise of employee stock options and the vesting of restricted stock units to be settled in stock, we issued less than 0.1 million shares for each of the years ended December 31, 2020, 2019 and 2018, pursuant to our employee stock purchase plan.