NOTE P. Net Income (Loss) Per Share Attributable To Common Stockholders

In the calculation of basic net income (loss) per share attributable to common stockholders, participating securities are allocated earnings based on actual dividend distributions received plus a proportionate share of undistributed net income attributable to common stockholders, if any, after recognizing distributed earnings. The Company's participating securities do not participate in undistributed net losses because they are not contractually obligated to do so. The computation of diluted net income (loss) per share attributable to common stockholders reflects the potential dilution that could occur if securities or other contracts to issue common stock that are dilutive were exercised or converted into common stock or resulted in the issuance of common stock that would then share in the earnings of the Company. During periods in which the Company realizes a loss from continuing operations attributable to common stockholders, securities or other contracts to issue common stock would not be dilutive to net loss per share and conversion into common stock is assumed not to occur. Diluted net income (loss) per share is calculated under both the two-class method and the treasury stock method and the more dilutive of the two calculations is presented. For each of the three years in the period ended December 31, 2011, the two-class method of calculating the Company's diluted net income (loss) per share was more dilutive than the treasury stock method.

The Company's basic net income (loss) per share attributable to common stockholders is computed as (i) net income (loss) attributable to common stockholders, (ii) less participating share- and unit-based basic earnings (iii) divided by weighted average basic shares outstanding. The Company's diluted net income (loss) per share attributable to common stockholders is computed as (i) basic net income (loss) attributable to common stockholders, (ii) plus diluted adjustments to participating undistributed earnings (iii) divided by weighted average diluted shares outstanding.

The following table is a reconciliation of the Company's net income (loss) attributable to common stockholders to basic net income (loss) attributable to common stockholders and to diluted net income (loss) attributable to common stockholders for the years ended December 31, 2011, 2010 and 2009:


	Year Ended December 31, 2011
	Continuing Operations			Discontinued Operations			Total
	(in thousands)
Net income (loss) attributable to common stockholders	$	411,337		$	423,152		$	834,489
Participating basic earnings (a)		(7,482	)		(7,696	)		(15,178	)

Basic income attributable to common stockholders		403,855			415,456			819,311
Reallocation of participating earnings (a)		190			195			385

Diluted income attributable to common stockholders	$	404,045		$	415,651		$	819,696


	Year Ended December 31, 2010
	Continuing Operations			Discontinued Operations			Total
	(in thousands)
Net income (loss) attributable to common stockholders	$	471,158		$	134,050		$	605,208
Participating basic earnings (a)		(10,818	)		(3,078	)		(13,896	)

Basic income attributable to common stockholders		460,340			130,972			591,312
Reallocation of participating earnings (a)		140			40			180

Diluted income attributable to common stockholders	$	460,480		$	131,012		$	591,492


	Year Ended December 31, 2009
	Continuing Operations			Discontinued Operations		Total
	(in thousands)
Net income (loss) attributable to common stockholders	$	(151,822	)	$	99,716	$	(52,106	)
Participating basic earnings (a)		(571	)		375		(196	)

Basic net income (loss) attributable to common stockholders		(152,393	)		100,091		(52,302	)
Reallocation of participating earnings (a)		—			—		—

Diluted income (loss) attributable to common stockholders	$	(152,393	)	$	100,091	$	(52,302	)

(a)

Unvested restricted stock awards and Pioneer Southwest phantom unit awards represent participating securities because they participate in nonforfeitable dividends or distributions with the common equity owners of the Company or Pioneer Southwest, as applicable. Participating share- and unit-based earnings represent the distributed and undistributed earnings of the Company attributable to the participating securities. Unvested restricted stock awards and phantom unit awards do not participate in undistributed net losses as they are not contractually obligated to do so.

The following table is a reconciliation of basic weighted average common shares outstanding to diluted weighted average common shares outstanding for the years ended December 31, 2011, 2010 and 2009:


	Year Ended December 31,
	2011		2010		2009
	(in thousands)
Weighted average common shares outstanding:
Basic		116,904		115,062		114,176
Dilutive common stock options (a)		190		212		—
Contingently issuable—performance shares (a)		424		646		—
Convertible notes dilution (b)		1,697		410		—


Diluted		119,215		116,330		114,176

(a)

Diluted earnings per share were calculated using the two-class method for the years ended December 31, 2011, 2010 and 2009. The following common stock equivalents were excluded from the diluted loss per share calculations for the year ended 2009 because they would have been anti-dilutive to the calculations: 173,915 outstanding options to purchase the Company's common stock and 223,969 performance shares.

(b)

During January 2008, the Company issued $500 million of 2.875% Convertible Senior Notes. Weighted average common shares outstanding have been increased to reflect the dilutive effect that would have resulted if the 2.875% Convertible Senior Notes had qualified for and been converted during the years ended December 31, 2011 and 2010, respectively. The 2.875% Convertible Senior Notes were not dilutive to the per share calculations of 2009.