Pensions and Postretirement Benefits

Our net periodic pension expense (income) for the three and six months ended May 31, 2014 and 2013 was comprised of the following (in thousands):



	Three months ended May 31,						Six months ended May 31,
	2014			2013			2014			2013
Service costs incurred	$	3,048		$	2,608		$	6,093		$	5,206
Interest costs on projected benefit obligation	2,140			1,768			4,241			3,461
Expected return on plan assets	(2,134		)	(1,903		)	(4,224		)	(3,724		)
Amortization of prior service credit	(338		)	(336		)	(676		)	(672		)
Amortization of transitional obligation	11			—			22			—
Net periodic pension expense	$	2,727		$	2,137		$	5,456		$	4,271

Our net periodic postretirement expense was comprised of the following for the three and six months ended May 31, 2014 and 2013 (in thousands):



	Three months ended May 31,				Six months ended May 31,
	2014		2013		2014		2013
Service costs incurred	$	4	$	5	$	8	$	11
Interest costs	103		100		206		200
Net periodic postretirement expense	$	107	$	105	$	214	$	211

We plan to freeze future accruals to our U.S. Retirement Income Plan (U.S. RIP) effective July 11, 2014. The financial impact of this change will be determined through the remeasurement process in the third quarter of 2014, but we do not believe that the remeasurement will have a material impact on our consolidated financial statements. We plan to provide an annual company non-elective contribution to the 401(k) accounts of affected eligible employees if they are active employees at the end of the calendar year.