2013, was a net liability of approximately $2.4 billion. An increase in the discount rate would decrease the pension obligation, thus changing the funded status of a plan. At December 31, 2013, the company used a discount rate of 4.3 percent to measure the obligations for the U.S. pension plans. As an indication of the sensitivity of pension liabilities to the discount rate assumption, a 0.25 percent increase in the discount rate applied to the company’s primary U.S. pension plan, which accounted for about 59 percent of the companywide pension obligation, would have reduced the plan obligation by approximately $345 million, which would have increased the plan’s overfunded status from approximately $0.4 billion to $0.7 billion.

For the company’s OPEB plans, expense for 2013 was $218 million, and the total liability, which reflected the unfunded status of the plans at the end of 2013, was $3.1 billion. For the main U.S. OPEB plan, the company used a 3.9 percent discount rate to measure expense in 2013, and a 4.7 percent discount rate to measure the benefit obligations at December 31, 2013. Discount rate changes, similar to those used in the pension sensitivity analysis, resulted in an immaterial impact on 2013 OPEB expense and OPEB liabilities at the end of 2013. For information on the sensitivity of the health care cost-trend rate, refer to FS-51 in Note 21 under the heading “Other Benefit Assumptions.”

Differences between the various assumptions used to determine expense and the funded status of each plan and actual experience are included in actuarial gain/loss. Refer to page FS-50 in Note 21 for a description of the method used to amortize the $5.2 billion of before-tax actuarial losses recorded by the company as of December 31, 2013, and an estimate of the costs to be recognized in expense during 2014. In addition, information related to company contributions is included on Page FS-53 in Note 21 under the heading “Cash Contributions and Benefit Payments.”

Contingent Losses Management also makes judgments and estimates in recording liabilities for claims, litigation, tax matters and environmental remediation. Actual costs can frequently vary from estimates for a variety of reasons. For example, the costs for settlement of claims and litigation can vary from estimates based on differing interpretations of laws, opinions on culpability and assessments on the amount of damages. Similarly, liabilities for environmental remediation are subject to change because of changes in laws, regulations and their interpretation, the determination of additional information on the extent and nature of site contamination, and improvements in technology.

Under the accounting rules, a liability is generally recorded for these types of contingencies if management determines the loss to be both probable and estimable. The company generally reports these losses as “Operating expenses” or “Selling, general and administrative expenses” on the Consolidated Statement of Income. An exception to this handling is for income tax matters, for which benefits are recognized only if management determines the tax position is “more likely than not” (i.e., likelihood