Company: CENX
Filing Date: 2025-03-03
Form Type: 10-K
Source: 0000949157-25-000024
Chunk: 89

Company: CENTURY ALUMINUM CO
Filing Date: 2025-03-03
Form: 10-K
Item: Item 7
Chunk 89
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 assumptions about future selling prices and the costs to complete our inventory during the period in which it will be sold.

Our assumptions are subject to inherent uncertainties given the volatility surrounding the market price for primary aluminum sales and the market price for our major inputs, alumina and electrical power. 

Although we believe that the assumptions used to estimate the market value of our inventory are reasonable, actual market conditions at the time our inventory is sold may be more or less favorable than management’s current estimates.

Pension and Other Postretirement Benefit Liabilities

We sponsor several pension and OPEB plans. Our liabilities under these defined benefit plans are determined using methodologies that involve several actuarial assumptions, the most significant of which are the discount rate and the long-term rate of return on plan assets. We review our actuarial assumptions on an annual basis and make modifications to the assumptions when appropriate.

Discount Rate Selection

We select a discount rate for purposes of measuring obligations under defined benefit plans by matching cash flows separately for each plan to the yields on high-quality zero coupon bonds. We use the Ryan Above Median Yield Curve (the "Ryan Curve"). We believe the projected cash flows used to determine the Ryan Curve rate provide a good approximation of the timing and amounts of our defined benefit payments under our plans and no adjustment to the Ryan Curve rate has been made.

Weighted Average Discount Rate Assumption for:20242023Pension plans5.99%5.19%OPEB plans5.62%5.19%

A change of a half percentage point in the discount rate for our defined benefit plans would have the following effects on our obligations under these plans as of December 31, 2024:

Effect of changes in the discount rates on the Projected Benefit Obligations for:50 basis point increase50 basis point decrease (dollars in millions)Pension plans$(13.3)$14.7 OPEB plans(2.9)3.1 

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Long-term Rate of Return on Plan Assets Assumption

Our expected long-term rate of return on plan assets is derived from our asset allocation strategies and anticipated future long-term performance of individual asset classes. Our analysis gives consideration to recent plan performance and historical returns; however, the assumptions are primarily based on long-term, prospective rates of return. The weighted average long-term rate of return on plan assets for our defined benefit pension plans is 7.28% for 2024.

Based on information provided by independent actuaries and other relevant sources, the Company believes that