Components of net benefit expense (income) were as follows: Pension 2020 2019 2018 Service cost $ 19 $ 21  $ 24  Interest cost 65 82  74  Expected return on plan assets (134) (143) (144) Amortization of prior service cost — 1  —  Recognized net actuarial (gain) loss 98 120  (104) Special termination benefits — —  2  Curtailment gains — —  (2) Settlement charges 43 28  —  Net periodic benefit expense (income) $ 91 $ 109  $ (150) to health care coverage through a private exchange and offer a health reimbursement account to subsidize benefits for a select group of such retirees. We use the fiscal year end as the measurement date for the benefit plans. The components of net periodic benefit expense (income) other than the service cost component associated with continuing operations are included in Other expenses / (income) in the Consolidated Statements of Earnings. The settlement charges of $43 in 2020 resulted from the level of lump sum distributions associated with a U.S. pension plan and a Canadian pension plan. The settlement charge of $28 in 2019 resulted from the level of lump sum distributions associated with a U.S. pension plan. The special termination benefits of $2 related to the planned closure of the manufacturing facility in Toronto, Ontario, and were included in Restructuring charges. Net periodic benefit expense (income) associated with discontinued operations was not material in 2020, $13 in 2019, and ($4) in 2018. Beginning in 2018, we changed the method we use to estimate the service and interest cost components of net periodic benefit expense (income). We elected to use a full yield curve approach to estimate service cost and interest cost by applying the specific spot rates along the yield curve used to determine the benefit obligation of the relevant projected cash flows. Previously, we estimated service cost and interest cost using a single weighted-average discount rate derived from the yield curve used to measure the benefit obligation at the beginning of the period. We made this change to provide a more precise measurement of service cost and interest cost by improving the correlation between projected benefit cash flows and the corresponding spot yield curve rates. This change does not affect the measurement of our benefit obligations. We accounted for this change prospectively in 2018 as a change in accounting estimate. As a result of this change, net periodic benefit income increased by approximately $17 in 2018, compared to what the net periodic benefit income would have been under the previous method. The components of net periodic benefit expense (income) other than the service cost component associated with continuing operations are included in Other expenses / (income) in the Consolidated Statements of Earnings. The estimated prior service credit that will be amortized from Accumulated other comprehensive loss into net periodic postretirement expense during 2021 is $5. The prior service credit is primarily related to the amendments in July 2016, July 2017, and July 2018. 59 Postretirement 2020 2019 2018 Service cost $ 1 $ 1  $ 1  Interest cost 6 8  7  Amortization of prior service credit (28) (29) (27) Recognized net actuarial (gain) loss 23 14  (16) Net periodic benefit expense (income) $ 2 $ (6) $ (35)