Incentive Plans

Stock-based compensation

For the three months ended March 31, 2014, the Company recorded $31 million of stock-based compensation expense for all plans, as compared to $28 million for the same period of 2013. As of March 31, 2014, there was $211 million of unrecognized compensation expense related to unvested share-based compensation plan awards, including $57 million attributable to stock-based awards that are expected to be settled on their vesting date in cash, rather than in equity shares ("Liability Awards"). The unrecognized compensation expense will be recognized over the remaining vesting periods of the awards, which is a period of less than three years on a weighted average basis. As of March 31, 2014 and December 31, 2013, accounts payable – due to affiliates includes $8 million and $33 million, respectively, of liabilities attributable to Liability Awards.

The following table summarizes the activity that occurred during the three months ended March 31, 2014, for each type of share-based incentive award issued by Pioneer:



	Restricted Stock Equity Awards		Restricted Stock Liability Awards		Performance Units		Stock Options
Outstanding as of December 31, 2013	1,371,207		422,382		134,476		289,927
Awards granted	380,586		132,803		67,182		—
Awards vested	(406,302	)	(181,131	)	(898	)	—
Options exercised	—		—		—		(32,098	)
Awards forfeited	(2,670	)	(6,356	)	—		—
Outstanding as of March 31, 2014	1,342,821		367,698		200,760		257,829

Postretirement Benefit Obligations

As of March 31, 2014 and December 31, 2013, the Company had $6 million and $8 million, respectively, of unfunded accumulated postretirement benefit obligations. These obligations are comprised of five unfunded plans, of which four relate to predecessor entities that the Company acquired in prior years. Other than the Company's retirement plan, the participants of these plans are not current employees of the Company. The plans had no assets as of March 31, 2014 or December 31, 2013.