10. Earnings per share attributable to stockholders

Basic EPS attributable to stockholders was calculated by dividing the net income attributable to stockholders by the weighted average (“WA”) number of common shares outstanding. Diluted EPS attributable to stockholders was calculated by dividing the net income attributable to stockholders after giving effect to outstanding dilutive stock options and PSUs by the WA number of shares outstanding adjusted for all dilutive securities.



	Net income	WA
	attributable to	number		Per share
Year ended December 31, 2017	stockholders	of shares		amount
Basic	75,027	107,044,348	$	0.70
Effect of dilutive securities:
PSUs	(152)	353,880		-
Stock options	-	714,923		(0.01)
Diluted	74,875	108,113,151	$	0.69



	Net income	WA
	attributable to	number		Per share
Year ended December 31, 2016	stockholders	of shares		amount
Basic	91,832	106,630,323	$	0.86
Effect of dilutive securities:
PSUs	-	91,997		-
Stock options	-	735,474		(0.01)
Diluted	91,832	107,457,794	$	0.85



	Net income	WA
	attributable to	number		Per share
Year ended December 31, 2015	stockholders	of shares		amount
Basic	136,214	107,075,845	$	1.27
Effect of dilutive securities:
Stock options	-	356,629		-
Diluted	136,214	107,432,474	$	1.27

In respect of PSUs awarded under the sign-on grant PSUs and the senior executive and employee PSU plans (described in note 28), performance and market conditions, depending on their outcome at the end of the contingency period, can reduce the number of vested awards to nil or to a maximum of 200% of the number of outstanding PSUs. For the year ended December 31, 2017, nil PSUs to purchase common shares were outstanding but excluded from the calculation of diluted EPS attributable to stockholders as they were anti-dilutive (2016: 173,754; 2015: nil). For the year ended December 31, 2017, stock options to purchase 668,900 common shares were outstanding but excluded from the calculation of diluted EPS attributable to stockholders as they were anti-dilutive (2016: 752,197; 2015: 253,839).