12. Capital Stock

The Company's authorized capital stock consists of 25 million shares of preferred stock, par value $.001 per share, 500 million shares of Class A common stock, par value $.001 per share, and 100 million shares of Class B common stock, par value $.001 per share. The shares of Class A common stock and Class B common stock are identical in all respects, except for voting rights and certain conversion rights and transfer restrictions, as follows: (1) each share of Class A common stock entitles the holder to one vote on matters submitted to a vote of the Company's stockholders and each share of Class B common stock entitles the holder to ten votes on each such matter; (2) stock dividends of Class A common stock may be paid only to holders of Class A common stock and stock dividends of Class B common stock may be paid only to holders of Class B common stock; (3) if a holder of Class B common stock transfers such shares to a person other than a permitted transferee, as defined in the Company's Certificate of Incorporation, such shares will be converted automatically into shares of Class A common stock; and (4) Class A common stock has no conversion rights; however, each share of Class B common stock is convertible into one share of Class A common stock, in whole or in part, at any time at the option of the holder. All outstanding Class B shares have been converted to Class A shares. As of December 31, 2016 and 2017, there were no preferred or Class B common shares outstanding.

Weighted-average common shares outstanding

The following is a reconciliation of the weighted-average common shares outstanding for purposes of computing basic and diluted net income per share (in thousands):

	Year Ended December 31,
	2015		2016		2017

Basic weighted-average common shares outstanding		57,997		55,412		52,806
Effect of dilutive securities: Stock awards and options		1,060		683		1,110
Convertible note		—		2		936
Diluted weighted-average common shares outstanding		59,057		56,097		54,852

For the years ended December 31, 2015, 2016 and 2017, other stock options totaling 1.8 million, 2.0 million and 0.4 million, respectively, were excluded from the calculation of diluted earnings per share because they were anti-dilutive. The convertible note has a dilutive impact on EPS when the average market price of the Company's common stock for a given period exceeds the initial conversion price. See Note 10 for discussion of initial conversion price and conversion rate.

Repurchases of common stock

In 1998, the Company's board of directors approved a stock repurchase plan authorizing the Company to repurchase $10.0 million of its outstanding shares of Class A common stock on the open market or in private transactions. The Company's board from time to time increased the amount authorized under the 1998 stock repurchase plan, including an increase of $400.0 million announced in August 2013. In October 2015, the Company's board terminated the 1998 stock repurchase plan and approved a new repurchase plan with an initial authorization amount of $500.0 million. The repurchases are used primarily for strategic initiatives and to offset dilution from the Company's equity incentive plans and from conversion of the Convertible Notes. During the years ended December 31, 2015, 2016 and 2017, the Company repurchased 3.8 million, 4.5 million and 1.2 million shares of Class A common stock for an aggregate price of $164.1 million, $247.2 million and $71.7 million, respectively. At December 31, 2017, $128.0 million was available for repurchases under the 2015 stock repurchase plan.