8. Retirement Plans

Components of net periodic pension cost consisted of the following:

	Three Months Ended
	March 31,
	2018			2017
	(In millions)
Service cost	$	14		$	14
Interest cost		23			26
Expected return on plan assets		(49	)		(41	)
Amortization of unrecognized net actuarial losses		12			17
Curtailment gains		(2	)		—
Pension (benefit) expense	$	(2	)	$	16

In 2018, we recorded curtailment gains of $18 million to Accumulated other comprehensive income (loss) and $2 million to the Statement of Consolidated Income following workforce reductions in the first quarter. In connection with this curtailment, as required under accounting standards, we remeasured our U.S. retirement plans and recorded a total decrease of $125 million in the Corporation’s U.S. pension liabilities. This reduction was primarily driven by a change in weighted average discount rates used to measure the liabilities. There was no change to the weighted average expected long-term rate of return on plan assets.

For the full year 2018, we now forecast pension service costs of approximately $45 million, interest cost of approximately $95 million, amortization of unrecognized net actuarial losses of approximately $40 million, and estimated expected return on plan assets of approximately $195 million. Net non-service pension costs included in Other, net in the Statement of Consolidated Income for the three months ended March 31, 2018 and 2017, was income of $16 million and expense of $2 million, respectively.

In 2018, we expect to contribute $44 million to our funded pension plans. Through March 31, 2018, we have contributed $14 million to these plans.