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 include the effect of certain stock options.



	Three Months Ended September 30,						Nine Months Ended September 30,
	2017			2016			2017			2016
Net income attributable to Westlake Chemical Corporation	$	210,832		$	65,662		$	501,849		$	299,914
Less:
Net income attributable to participating securities	(1,117		)	(294		)	(2,630		)	(1,347		)
Net income attributable to common shareholders	$	209,715		$	65,368		$	499,219		$	298,567

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 September 30,				Nine Months Ended September 30,
	2017		2016		2017		2016
Weighted average common shares—basic	129,069,186		128,793,661		129,033,597		129,519,577
Plus incremental shares from:
Assumed exercise of options	819,782		586,295		756,368		584,320
Weighted average common shares—diluted	129,888,968		129,379,956		129,789,965		130,103,897

Earnings per common share attributable to Westlake Chemical Corporation:
Basic	$	1.62	$	0.51	$	3.87	$	2.31
Diluted	$	1.61	$	0.51	$	3.85	$	2.29

Excluded from the computation of diluted earnings per share are options to purchase 335,276 and 620,010 shares of common stock for the three months ended September 30, 2017 and 2016, respectively, and 291,888 and 577,254 shares of common stock for the nine months ended September 30, 2017 and 2016, respectively. These options were outstanding during the periods reported but were excluded because the effect of including them would have been antidilutive.