Earnings per Share

The Company has unvested restricted stock units outstanding that are considered participating securities and, therefore, computes basic and diluted earnings per share under the two-class method. Basic earnings per share for the periods are based upon the weighted average number of shares of common stock outstanding during the periods. Diluted earnings per share includes the effect of certain stock options.



	Three Months Ended June 30,						Six Months Ended June 30,
	2018			2017			2018			2017
Net income attributable to Westlake Chemical Corporation	$	278		$	153		$	565		$	291
Less:
Net income attributable to participating securities	(2		)	(1		)	(3		)	(2		)
Net income attributable to common shareholders	$	276		$	152		$	562		$	289

The following table reconciles the denominator for the basic and diluted earnings per share computations shown in the consolidated statements of operations:



	Three Months Ended June 30,				Six Months Ended June 30,
	2018		2017		2018		2017
Weighted average common shares—basic	129,624,291		129,051,227		129,554,528		129,015,507
Plus incremental shares from:
Assumed exercise of options	682,324		735,487		694,556		724,136
Weighted average common shares—diluted	130,306,615		129,786,714		130,249,084		129,739,643

Earnings per common share attributable to Westlake Chemical Corporation:
Basic	$	2.13	$	1.18	$	4.34	$	2.24
Diluted	$	2.12	$	1.17	$	4.31	$	2.23

Excluded from the computation of diluted earnings per share are options to purchase 172,642 and 583,585 shares of common stock for the three months ended June 30, 2018 and 2017, respectively, and 128,892 and 511,085 shares of common stock for the six months ended June 30, 2018 and 2017, respectively. These options were outstanding during the periods reported but were excluded because the effect of including them would have been antidilutive.