4. Per Share Data

Basic earnings per share are computed using net income attributable to common shareholders and the weighted average number of common shares outstanding. Diluted earnings per share reflect common shares issuable from the assumed conversion of common share options and share awards granted and units convertible into common shares. Only those items having a dilutive impact on our basic earnings per share are included in diluted earnings per share. Our unvested share-based awards are considered participating securities and are reflected in the calculation of basic and diluted earnings per share using the two-class method. The number of common share equivalent securities excluded from the diluted earnings per share calculation was approximately 2.1 million, 1.5 million, and 2.4 million for the years ended December 31, 2018, 2017, and 2016, respectively. These securities, which include common share options and share awards granted and units convertible into common shares, were excluded from the diluted earnings per share calculation as they are anti-dilutive.

The following table presents information necessary to calculate basic and diluted earnings per share for the periods indicated:



	Year Ended December 31,
(in thousands, except per share amounts)	2018			2017			2016
Earnings per common share calculation – basic
Income from continuing operations attributable to common shareholders	$	156,128		$	196,422		$	436,981
Amount allocated to participating securities	(1,107		)	(660		)	(6,304		)
Income from continuing operations attributable to common shareholders, net of amount allocated to participating securities	$	155,021		$	195,762		$	430,677
Discontinued operations, including gain on sale, attributable to common shareholders	—			—			382,842
Net income attributable to common shareholders – basic	$	155,021		$	195,762		$	813,519

Earnings per common share from continuing operations	$	1.63		$	2.14		$	4.81
Earnings per common share from discontinued operations	—			—			4.27
Total earnings per common share – basic	$	1.63		$	2.14		$	9.08

Weighted average number of common shares outstanding – basic	95,208			91,499			89,580



	Year Ended December 31,
(in thousands, except per share amounts)	2018		2017		2016
Earnings per common share calculation – diluted
Income from continuing operations attributable to common shareholders, net of amount allocated to participating securities	$	155,021	$	195,762	$	430,677
Income allocated to common units from continuing operations	—		1,174		—
Income from continuing operations attributable to common shareholders, as adjusted	$	155,021	$	196,936	$	430,677
Discontinued operations, including gain on sale, attributable to common shareholders	—		—		382,842
Net income attributable to common shareholders – diluted	$	155,021	$	196,936	$	813,519

Earnings per common share from continuing operations	$	1.63	$	2.13	$	4.79
Earnings per common share from discontinued operations	—		—		4.26
Total earnings per common share – diluted	$	1.63	$	2.13	$	9.05

Weighted average number of common shares outstanding – basic	95,208		91,499		89,580
Incremental shares issuable from assumed conversion of:
Common share options and share awards granted	158		211		323
Common units	—		805		—
Weighted average number of common shares outstanding – diluted	95,366		92,515		89,903