Earnings Per Share

Basic net income per share (“EPS”) is calculated by dividing net income attributable to common stockholders by the weighted average shares outstanding during the period. Diluted EPS is calculated by adjusting weighted average shares outstanding for the dilutive effect of potential common shares, determined using the treasury-stock method. For purposes of the diluted EPS calculation, stock options, restricted stock and restricted stock unit awards are considered to be potential common shares. Performance-based restricted stock units are not included in the calculation of diluted EPS until they are contingently issuable.

The basic and diluted EPS calculations for the years ended December 31, 2018, 2017 and 2016 are presented below:



	Year Ended December 31,
(in thousands, except per share amounts)	2018		2017		2016
Income attributable to common stockholders	$	119,738	$	57,425	$	30,880

Weighted average common shares outstanding, basic	67,273		66,900		66,055
Effect of dilutive securities:
Restricted stock units	324		235		129
Stock options	135		204		218
Restricted stock	16		65		207
Weighted average common shares outstanding, diluted	67,748		67,404		66,609

Basic income per common share	$	1.78	$	0.86	$	0.47
Diluted income per common share	$	1.77	$	0.85	$	0.46

The following table provides the securities that could potentially dilute EPS in the future, but were not included in the computation of diluted EPS for the periods presented because to do so would have been anti-dilutive. The amounts included in this table exclude performance-based restricted stock units. As of December 31, 2018, the number of currently outstanding performance-based restricted stock units that are issued upon vesting could range from zero to a maximum of 0.6 million.



	Year Ended December 31,
(in thousands)	2018	2017	2016
Restricted stock units	85	—	5
Stock options	349	—	469
Restricted stock	—	—	—