20. Basic and diluted earnings (loss) per share

Basic earnings (loss) per share is calculated by dividing net income (loss) by the weighted average common shares outstanding during their respective period. Diluted earnings (loss) per share is computed including dilutive potential shares as if they were outstanding shares during the year. Dilutive potential shares include shares that would be issued if all of the convertible debentures were converted into shares at January 1, 2015. Dilutive potential shares also include the weighted average number of shares, as of the date such notional units were granted, that would be issued if the unvested notional units outstanding under the LTIP were vested and redeemed for shares under the terms of the LTIP.

Because we reported a loss for the years ended December 31, 2015, 2014 and 2013, diluted earnings per share are equal to basic earnings per share as the inclusion of potentially dilutive shares in the computation is anti‑dilutive.

The following table sets forth the diluted net income and potentially dilutive shares utilized in the per share calculation for the years ended December 31, 2015, 2014 and 2013:


	2015		2014		2013
Numerator:
Loss from continuing operations attributable to Atlantic Power Corporation	$	(92.9)	$	(164.8)	$	(36.2)
Income (loss) from discontinued operations, net of tax		30.5		(12.6)		3.2
Net loss attributable to Atlantic Power Corporation	$	(62.4)	$	(177.4)	$	(33.0)
Denominator:
Weighted average basic shares outstanding		121.9		120.7		119.9
Dilutive potential shares:
Convertible debentures		22.7		27.7		27.7
LTIP notional units		0.2		0.3		0.7
Potentially dilutive shares		144.8		148.7		148.3
Diluted loss per share from continuing operations attributable to Atlantic Power Corporation	$	(0.76)	$	(1.37)	$	(0.30)
Diluted earnings (loss) per share from discontinued operations		0.25		(0.10)		0.02
Diluted loss per share attributable to Atlantic Power Corporation	$	(0.51)	$	(1.47)	$	(0.28)

Potentially dilutive shares from convertible debentures have been excluded from fully diluted shares in the years ended December 31, 2015, 2014 and 2013 because their impact would be anti‑dilutive.