Net income per share for the three and nine months ended September 30, 2019 and 2018 is computed by dividing net income by the weighted-average number of common shares outstanding during the reporting period. The Company computes the weighted-average number of common shares outstanding during the reporting period using the total number of shares of Class A common stock and Class B common stock outstanding as of the last day of the previous year end reporting period plus the weighted-average of any additional shares issued and outstanding during the reporting period.

The Company has two classes of common stock authorized: Class A common stock and Class B common stock. The rights of the holders of Class A and Class B common stock are identical, except with respect to voting and conversion. Each share of Class A common stock is entitled to one vote per share and each share of Class B common stock is entitled to ten votes per share. Each share of Class B common stock is convertible into one share of Class A common stock at the option of the holder at any time or automatically upon certain events described in the Company’s amended and restated certificate of incorporation, including on either the death or voluntary termination of the Company’s Chief Executive Officer. The Company allocates undistributed earnings attributable to common stock between the common stock classes on a one‑to‑one basis when computing net income per share. As a result, basic and diluted net income per share of Class A common stock and per share of Class B common stock are equivalent.

During the three and nine months ended September 30, 2019, holders of Class B common stock converted 200,000 shares of Class B common stock to Class A common stock. During the nine months ended September 30, 2018, holders of Class B common stock converted 7,534,710 shares of Class B common stock to Class A common stock.

Diluted net income per share gives effect to all potentially dilutive securities. Potential dilutive securities for the three and nine months ended September 30, 2019 and 2018 consist of shares of common stock issuable upon the exercise of stock options and shares of common stock issuable upon the vesting of restricted stock units (“RSUs”). The dilutive effect of these common stock equivalents is reflected in diluted earnings per share by application of the treasury stock method.

For the three and nine months ended September 30, 2019 and 2018, diluted net income per share was calculated by dividing net income by the weighted-average number of shares of common stock outstanding during the period plus the dilutive impact of stock options and shares of common stock issuable upon the vesting of RSUs.

The following table presents a reconciliation of the numerator and denominator used in the calculation of basic and diluted net income per share:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Numerator:
Net income	$	10,384	$	13,882	$	28,975	$	52,720
Denominator:
Weighted-average number of shares of common stock used in computing net income per share attributable to common stockholders — basic		111,662,949		109,628,692		111,257,271		108,367,270
Dilutive effect of share equivalents resulting from stock options		1,052,758		2,259,533		1,232,754		3,396,906
Dilutive effect of share equivalents resulting from unvested restricted stock units		649,068		1,713,190		899,670		1,586,974
Weighted-average number of shares of common stock used in computing net income per share — diluted		113,364,775		113,601,415		113,389,695		113,351,150
Net income per share attributable to common stockholders:
Basic	$	0.09	$	0.13	$	0.26	$	0.49
Diluted	$	0.09	$	0.12	$	0.26	$	0.47

The following potentially dilutive common stock equivalents have been excluded from the calculation of diluted weighted-average shares outstanding for the three and nine months ended September 30, 2019 and 2018, as their effect would have been anti-dilutive for the period presented: