INCOME TAXES

Income tax expense was $9 million for the three months ended March 31, 2015 compared to income tax expense of $50 million in the same period of 2014. For the three months ended March 31, 2015, changes in the effective tax rate from the prior period include tax planning strategies made available in the first quarter of 2015 resulting in releases of tax valuation allowances. The following table summarizes the difference between income tax expense at the United States statutory rate of 35% and the income tax expense at effective worldwide tax rates for the respective periods:



	Three Months Ended March 31,
Millions of dollars	2015			2014
Earnings before income taxes	$	207		$	214

Income tax expense computed at United States statutory tax rate	72			75
U.S. foreign income items, net of credits	(2		)	(12		)
Valuation allowance release	(58		)	—
Foreign government tax incentive (including BEFIEX in 2014)	(4		)	(5		)
Other	1			(8		)
Income tax expense computed at effective worldwide tax rates	$	9		$	50

At the end of each interim period, we make our best estimate of the effective tax rate expected to be applicable for the full fiscal year and the impact of discrete items, if any, and adjust the quarterly rate as necessary.