other post-retirement benefit liabilities but generally results in lower benefit expense in periods when the yield curve is upward sloping, which was the case in 2018. We accounted for this change as a change in accounting estimate and, accordingly, accounted for it on a prospective basis starting in 2018. A 100 basis point decrease (increase) in the weighted-average pension discount rate would increase (decrease) annual net periodic pension benefit expense by approximately $7 million and the December 31, 2020 pension liability would increase by approximately $108 million or decrease by approximately $91 million, respectively. Pension expense for defined benefit pension plans is expected to be approximately $6 million in 2021. Pension expense beyond 2021 will depend on future investment performance, our contributions to the pension trusts, changes in discount rates and various other factors related to the covered employees in the plans. Other Post-Employment Benefit Plans Changes in significant assumptions could affect consolidated expense and benefit obligations, particularly the discount rates used to calculate such obligations: We use the acquisition method of accounting for business acquisitions. Under the acquisition method, the results of operations of the acquired business have been included in the consolidated financial statements since the respective dates of the acquisitions. The assets acquired and liabilities assumed are recorded at their respective estimated fair values at the date of the acquisition. Any excess of the purchase price over the estimated fair values of the identifiable net assets acquired is recorded as goodwill. Significant judgment is often required in estimating the fair value of assets acquired, particularly intangible assets. As a result, we normally obtain the assistance of a third-party valuation specialist in estimating fair values of tangible and intangible assets. The fair value estimates are based on available historical information and on expectations and assumptions about the future, considering the perspective of marketplace participants. While management believes those expectations and assumptions are reasonable, they are inherently uncertain. Unanticipated market or macroeconomic events and circumstances may occur, which could affect the accuracy or validity of the estimates and assumptions. Goodwill and indefinite-lived intangible assets are not amortized, but instead, are evaluated for impairment annually or more often if indicators of a potential impairment are present. Our annual impairment tests are conducted at the beginning of the fourth quarter. We test goodwill for impairment by performing either a qualitative or quantitative assessment. If we choose to perform a qualitative assessment, we evaluate economic, industry and company-specific factors in assessing the fair value of the related reporting unit. If we determine that it is more likely than not that the fair value of the reporting unit is less than its carrying value, a quantitative test is then performed. Otherwise, no further testing is required. For those reporting units tested using a quantitative approach, we compare the fair value of each reporting unit with the carrying amount of the reporting unit, including goodwill. If the estimated fair value of the reporting unit is less than the carrying amount of the reporting unit, impairment is indicated, requiring recognition of a goodwill impairment charge for the differential (up to the carrying value of goodwill). We test individual indefinite-lived intangible assets by comparing the estimated fair values with the book values of each asset. We determine the fair value of our reporting units and indefinite-lived intangible assets using an income approach. Under the income approach, we calculate the fair value of our reporting units and indefinite-lived intangible assets based on the present value of estimated future cash flows. Considerable management judgment is necessary to evaluate the impact of operating and macroeconomic changes and to estimate the future cash flows used to measure fair value. Our estimates of future cash flows consider past performance, current and anticipated market conditions and internal projections and operating plans which incorporate estimates for sales growth and profitability, and cash flows associated with taxes and capital spending. Additional assumptions include forecasted growth rates, estimated discount Table of Contents The Hershey Company | 2020 Form 10-K | Page 39 Business Acquisitions, Valuation and Impairment of Goodwill and Other Intangible Assets • Discount rate. The determination of the discount rate used to calculate the benefit obligations of the OPEB plans is discussed in the pension plans section above. A 100 basis point decrease (increase) in the discount rate assumption for these plans would not be material to the OPEB plans' consolidated expense and the December 31, 2020 benefit liability would increase by approximately $27 million or decrease by approximately $22 million, respectively.