6. INCOME TAXES

The components of income tax expense (benefit) are as follows:



	Year Ended December 31,
thousands	2015		2014			2013
Current income tax expense (benefit)
Federal income tax expense (benefit)	$	590	$	(1,729	)	$	(35,917	)
State income tax expense (benefit)	858		63			493
Total current income tax expense (benefit)	1,448		(1,666		)	(35,424		)
Deferred income tax expense (benefit)
Federal income tax expense (benefit)	348		10,612			40,846
State income tax expense (benefit)	1,584		2,713			(811		)
Total deferred income tax expense (benefit)	1,932		13,325			40,035
Total income tax expense (benefit)	$	3,380	$	11,659		$	4,611

Total income taxes differed from the amounts computed by applying the statutory income tax rate to income (loss) before income taxes. The sources of these differences are as follows:



	Year Ended December 31,
thousands except percentages	2015			2014			2013
Income (loss) before income taxes	$	(63,166	)	$	416,347		$	290,585
Statutory tax rate	—		%	—		%	—		%
Tax computed at statutory rate	$	—		$	—		$	—
Adjustments resulting from:
Federal taxes on income attributable to Anadarko’s investment in WES	942			8,988			5,344
State taxes on income attributable to Anadarko’s investment in WES (net of federal benefit)	27			190			626
Texas margin tax expense (benefit) ⁽¹⁾	2,411			2,481			(1,359		)
Income tax expense (benefit)	$	3,380		$	11,659		$	4,611
Effective tax rate	(5		)%	3		%	2		%


⁽¹⁾	Includes a reduction of $2.2 million in deferred state income taxes. Texas House Bill 32, signed into law in June 2015, reduced the Texas margin tax rates by 0.25%. The law became effective January 1, 2016. WGP is required to include the impact of the law change on its deferred state income taxes in the period enacted.

The tax effects of temporary differences that give rise to significant portions of deferred tax assets (liabilities) are as follows:



	December 31,
thousands	2015			2014
Depreciable property	$	(4,418	)	$	(44,725	)
Credit carryforwards	512			526
Other intangible assets	(2,070		)	(1,450		)
Other	13			7
Net long-term deferred income tax liabilities	$	(5,963	)	$	(45,642	)

Credit carryforwards, which are available for use on future income tax returns, consist of $0.5 million of state income tax credits that expire in 2026.