Incentive Plans

Stock-based compensation

For the three and six months ended June 30, 2015, the Company recorded $32 million and $61 million, respectively, of stock-based compensation expense for all plans, as compared to $33 million and $62 million for the same respective periods of 2014. As of June 30, 2015, there was $164 million of unrecognized compensation expense related to unvested share-based compensation plan awards, including $30 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 June 30, 2015 and December 31, 2014, accounts payable – due to affiliates includes $11 million and $23 million, respectively, of liabilities attributable to Liability Awards.

The following table summarizes the activity that occurred during the six months ended June 30, 2015, 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, 2014	1,233,539		328,087		154,733	199,058
Awards granted	435,462		158,726		82,431	—
Awards vested	(508,335	)	(173,759	)	—	—
Awards forfeited	(10,859	)	(13,997	)	—	—
Outstanding as of June 30, 2015	1,149,807		299,057		237,164	199,058