and losses reflected in income. There were no open foreign currency derivative contracts at December 31, 2018.

Interest Rates The company may enter into interest rate swaps from time to time as part of its overall strategy to manage the interest rate risk on its debt. Interest rate swaps, if any, are recorded at fair value on the balance sheet with resulting gains and losses reflected in income. At year-end 2018, the company had no interest rate swaps.

Transactions With Related Parties

Chevron enters into a number of business arrangements with related parties, principally its equity affiliates. These arrangements include long-term supply or offtake agreements and long-term purchase agreements. Refer to “Other Information” on page 70, in Note 14, Investments and Advances, for further discussion. Management believes these agreements have been negotiated on terms consistent with those that would have been negotiated with an unrelated party.

Litigation and Other Contingencies

MTBE Information related to methyl tertiary butyl ether (MTBE) matters is included on page 70 in Note 15 under the heading “MTBE.”

Ecuador Information related to Ecuador matters is included in Note 15 under the heading “Ecuador,” beginning on page 70.

Environmental The following table displays the annual changes to the company’s before-tax environmental remediation reserves, including those for federal Superfund sites and analogous sites under state laws.

The company records asset retirement obligations when there is a legal obligation associated with the retirement of long-lived assets and the liability can be reasonably estimated. These asset retirement obligations include costs related to environmental issues. The liability balance of approximately $14.1 billion for asset retirement obligations at year-end 2018 related primarily to upstream properties.

For the company’s other ongoing operating assets, such as refineries and chemicals facilities, no provisions are made for exit or cleanup costs that may be required when such assets reach the end of their useful lives unless a decision to sell or otherwise abandon the facility has been made, as the indeterminate settlement dates for the asset retirements prevent estimation of the fair value of the asset retirement obligation.

Refer to the discussion below for additional information on environmental matters and their impact on Chevron, and on the company's 2018 environmental expenditures. Refer to Note 23 on page 86 for additional discussion of environmental remediation provisions and year-end reserves. Refer also to Note 24 on page 88 for additional discussion of the company's asset retirement obligations.

Suspended Wells Information related to suspended wells is included in Note 20, Accounting for Suspended Exploratory Wells, beginning on page 79.

Income Taxes Information related to income tax contingencies is included on pages 74 through 76 in Note 16 and page 86 in Note 23 under the heading “Income Taxes.”

Other Contingencies Information related to other contingencies is included on page 87 in Note 23 to the Consolidated Financial Statements under the heading “Other Contingencies.”