Table of Contents E. Net periodic cost U.S. Pension Benefits Non-U.S. Pension Benefits Other Postretirement Benefits (Millions of dollars) 2018 2017 2016 2018 2017 2016 2018 2017 2016 Components of net periodic benefit cost: Service cost $ 125 $ 115 $ 119 $ 89 $ 95 $ 92 $ 83 $ 78 $ 82 Interest cost 534 525 517 96 101 117 125 130 131 Expected return on plan assets  1 (808) (734) (757) (221) (231) (227) (32) (37) (44) Curtailments and termination benefits — 9 6 (33) 15 1 (2) — (9) Amortization of prior service cost (credit)  2 — — — — (2) 3 (36) (23) (59) Actuarial loss (gain)  3 534 481 664 111 (195) 262 (150) 15 59 Net Periodic benefit cost (benefit)  4 $ 385 $ 396 $ 549 $ 42 $ (217) $ 248 $ (12) $ 163 $ 160 Other changes in plan assets and benefit obligations recognized in other comprehensive income (pre- tax): Current year prior service cost (credit) $ — $ — $ — $ 20 $ 3 $ (3) $ (20) $ (77) $ (184) Amortization of prior service (cost) credit — — — — 2 (3) 36 23 59 Total recognized in other comprehensive income — — — 20 5 (6) 16 (54) (125) Total recognized in net periodic cost and other comprehensive income $ 385 $ 396 $ 549 $ 62 $ (212) $ 242 $ 4 $ 109 $ 35 Weighted-average assumptions used to determine net cost: Discount rate used to measure service cost 3.7% 4.2% 4.5% 2.3% 2.4% 2.9% 3.5% 3.9% 4.2% Discount rate used to measure interest cost 3.2% 3.3% 3.4% 2.2% 2.3% 2.8% 3.2% 3.3% 3.3% Expected rate of return on plan assets  5  6.3% 6.7% 6.9% 5.2% 5.9% 6.1% 7.5% 7.5% 7.5% Rate of compensation increase 4.0% 4.0% 4.0% 4.0% 4.0% 3.6% 4.0% 4.0% 4.0% The discount rates used in the determination of our service and interest cost components are determined by utilizing a full yield curve approach which applies specific spot rates along the yield curve used in the determination of the benefit obligation to the relevant projected cash flows. Our U.S. expected long-term rate of return on plan assets is based on our estimate of long-term passive returns for equities and fixed income securities weighted by the allocation of our pension assets. Based on historical performance, we increase 1 Expected return on plan assets developed using the fair value of plan assets. 2 Prior service cost (credit) for both pension and other postretirement benefits is generally amortized using the straight-line method over the average remaining service period of active employees expected to receive benefits from the plan. For pension plans in which all or almost all of the plan's participants are inactive and other postretirement benefit plans in which all or almost all of the plan's participants are fully eligible for benefits under the plan, prior service cost (credit) is amortized using the straight-line method over the remaining life expectancy of those participants. 3 Actuarial loss (gain) represents the effects of actual results differing from our assumptions and the effects of changing assumptions. We recognize actuarial loss (gain) immediately through earnings upon the annual remeasurement in the fourth quarter, or on an interim basis as triggering events warrant remeasurement. 4 The service cost component of net periodic pension and other postretirement benefits cost (benefit) is included in Operating costs in Statement 1. All other components of net periodic pension and other postretirement benefits cost (benefit) are included in Other income (expense) in Statement 1. 5 The weighted-average rates for 2019 are 5.9 percent and 3.8 percent for U.S. and non-U.S. pension plans, respectively. 122