Income Taxes

3 Months Ended

Mar. 31, 2013

Disclosure Text Block [Abstract]

Income Taxes

12.  Income Taxes

The following summarizes income tax expense (benefit) and effective tax rates:

	Three Months Ended
	March 31,
millions except percentages	2013			2012
Income tax expense (benefit)	$	456		$	352
Effective tax rate		49	%		14	%

The increase from the 35% U.S. federal statutory rate for thethree months ended March 31, 2013, was primarily attributable to the tax impact from foreign operations and Algerian exceptional profits taxes.

The decrease from the 35% U.S. federal statutory rate for thethree months ended March 31, 2012, was primarily attributable to the non-taxable resolution of the Algeria exceptional profits tax dispute. This amount was partially offset by the tax impact from foreign operationsand Algerian exceptional profits taxes.