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The accumulated benefit obligation for our defined benefit pension plans was approximately $4.9 billion and $5.6 billion as of December 31, 2018, and December 31, 2017, respectively. The $130.8 million decrease in the net underfunded status of our aggregate pension and OPEB plans from December 31, 2017, to December 31, 2018, was primarily driven by the increase in discount rates. Our underfunded status also includes the impact of the High Court ruling in the U.K. related to equalizing pension benefits between men and women, which had an immaterial impact to our net underfunded status. 

As of December 31, 2018, our defined benefit plan in the U.K. and certain defined benefit plans in the U.S. and Canada were overfunded as a result of our ongoing de-risking strategy. Information for our defined benefit plans that had aggregate accumulated benefit obligations and projected benefit obligations in excess of plan assets as of December 31, 2018, is as follows: 

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Information for OPEB plans with an accumulated postretirement benefit obligation in excess of plan assets has been disclosed above in "Obligations and Changes in Funded Status" as all of our OPEB plans are unfunded. 

