15. Postretirement Benefits

We maintain a number of postretirement benefits, primarily consisting of healthcare and life insurance ("welfare") benefits, for certain eligible U.S. employees. Eligible employees consist of those who retired before March 31, 1999 and those who retired after March 31, 1999, but were an active employee as of that date, after meeting other age-related criteria. We also provide postretirement benefits for certain U.S. executives. Defined benefit plan obligations are measured as of the Company's fiscal year-end.

The net periodic expense (income) for our postretirement welfare benefits is as follows:


	Years Ended March 31,
(In millions)		2012			2011			2010
Service cost—benefits earned during the year	$	2		$	1		$	1
Interest cost on accumulated benefit obligation		7			8			9
Amortization of unrecognized actuarial loss (gain) and
prior service costs		(1	)		(4	)		(25	)
Net periodic postretirement expense (income)	$	8		$	5		$	(15	)

Information regarding the changes in benefit obligations for our postretirement welfare plans is as follows:


	Years Ended March 31,
(In millions)		2012			2011
Benefit obligation at beginning of period	$	152		$	154
Service cost		2			1
Interest cost		7			8
Actuarial loss (gain)		(4	)		2
Benefit payments		(13	)		(13	)
Benefit obligation at end of period	$	144		$	152

The components of the amount recognized in accumulated other comprehensive income for the Company's other postretirement benefits at March 31, 2012 and 2011 were net actuarial losses of $2 million and $5 million and net prior service credits of $2 million and $2 million. Other changes in benefit obligations recognized in other comprehensive income were net actuarial gain of $3 million in 2012 and losses of $6 million and $51 million in 2011 and 2010.

We estimate that the amortization of the actuarial loss from stockholders' equity to other postretirement expense in 2013 will be $1 million. Comparable 2012 amounts were $1 million.

Other postretirement benefits are funded as claims are paid. Expected benefit payments for our postretirement welfare benefit plans, net of expected Medicare subsidy receipts of $1 million annually, are as follows: $11 million annually for 2013 to 2017 and $50 million cumulatively for 2018 through 2022. Expected benefit payments are based on the same assumptions used to measure the benefit obligations and include estimated future employee service. Expected contributions to be made for our postretirement welfare benefit plans are $13 million for 2013.

Weighted-average discount rates used to estimate postretirement welfare benefit expenses were 5.09%, 5.33% and 7.86% for 2012, 2011 and 2010. Weighted-average discount rates for the actuarial present value of benefit obligations were 4.44%, 5.09% and 5.33% for 2012, 2011 and 2010.

Actuarial gain or loss for the postretirement welfare benefit plan is amortized to income or expense over a three-year period. The assumed healthcare cost trends used in measuring the accumulated postretirement benefit obligation were 8.0% and 8.5% for prescription drugs, 7.5% and 7.5% for medical and 5.5% and 5.8% for dental in 2012 and 2011. For 2012, 2011 and 2010, a one-percentage-point increase or decrease in the assumed healthcare cost trend rate would not have a material impact on the postretirement benefit obligations.