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Basic and diluted earnings (loss) per share | 12 Months Ended
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Dec. 31, 2012
Basic and diluted earnings (loss) per share |
Basic and diluted earnings (loss) per share | 18. 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, 2012. 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, 2012, 2011 and 2010, 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, 2012, 2011 and 2010:
|  | 2012 |  | 2011 |  | 2010 |
--- | --- | --- | --- | --- | --- | --- | ---
Numerator: |  |  |  |  |  |  |  |  |  |
Loss from continuing operations attributable to Atlantic Power Corporation |  | $ | (129,235 | ) | $ | (74,585 | ) | $ | (27,879 | )
Income from discontinued operations, net of tax |  |  | 16,459 |  |  | 36,177 |  |  | 24,127 |
Net loss attributable to Atlantic Power Corporation |  | $ | (112,776 | ) | $ | (38,408 | ) | $ | (3,752 | )
Denominator: |  |  |  |  |  |  |  |  |  |
Weighted average basic shares outstanding |  |  | 116,426 |  |  | 77,466 |  |  | 61,706 |
Dilutive potential shares: |  |  |  |  |  |  |  |  |  |
Convertible debentures |  |  | 17,353 |  |  | 13,962 |  |  | 12,339 |
LTIP notional units |  |  | 489 |  |  | 438 |  |  | 542 |
Potentially dilutive shares |  |  | 134,268 |  |  | 91,866 |  |  | 74,587 |
Diluted loss per share from continuing operations attributable to Atlantic Power Corporation |  | $ | (1.11 | ) | $ | (0.96 | ) | $ | (0.45 | )
Diluted earnings per share from discontinued operations |  |  | 0.14 |  |  | 0.46 |  |  | 0.39 |
Diluted loss per share attributable to Atlantic Power Corporation |  | $ | (0.97 | ) | $ | (0.50 | ) | $ | (0.06 | )
Potentially dilutive shares from convertible debentures and potentially dilutive shares from LTIP notional units have been excluded from fully diluted shares in the years ended December 31, 2012, 2011 and 2010 because their impact would be anti-dilutive.

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- Definition The entire disclosure for earnings per share. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=7655603&loc=d3e1252-109256 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 55 -Paragraph 52 -URI http://asc.fasb.org/extlink&oid=16381557&loc=d3e4984-109258 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=7655603&loc=d3e1278-109256 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 128 -Paragraph 40 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.21) -URI http://asc.fasb.org/extlink&oid=6880815&loc=d3e20235-122688 + Details
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