deteriorate.

Worldwide downstream spending in 2018 is estimated to be $2.2 billion, with $1.4 billion estimated for projects in the United States.

Investments in technology companies and other corporate businesses in 2018 are budgeted at $0.3 billion.

Noncontrolling Interests The company had noncontrolling interests of $1.2 billion at December 31, 2017 and December 31, 2016. Distributions to noncontrolling interests totaled $78 million and $63 million in 2017 and 2016, respectively.

Pension Obligations Information related to pension plan contributions is included on page 82 in Note 23, Employee Benefit Plans, under the heading “Cash Contributions and Benefit Payments.”

Financial Ratios

Current Ratio Current assets divided by current liabilities, which indicates the company’s ability to repay its short-term liabilities with short-term assets. The current ratio in all periods was adversely affected by the fact that Chevron’s inventories are valued on a last-in, first-out basis. At year-end 2017, the book value of inventory was lower than replacement costs, based on average acquisition costs during the year, by approximately $3.9 billion.

Interest Coverage Ratio Income before income tax expense, plus interest and debt expense and amortization of capitalized interest, less net income attributable to noncontrolling interests, divided by before-tax interest costs. This ratio indicates the company’s ability to pay interest on outstanding debt. The company’s interest coverage ratio in 2017 was higher than 2016 and 2015 due to higher income.

Debt Ratio Total debt as a percentage of total debt plus Chevron Corporation Stockholders' Equity, which indicates the company’s leverage. The company's debt ratio was 20.7 percent at year-end 2017, compared with 24.1 percent and 20.2 percent at year-end 2016 and 2015, respectively.

Off-Balance-Sheet Arrangements, Contractual Obligations, Guarantees and Other Contingencies

Long-Term Unconditional Purchase Obligations and Commitments, Including Throughput and Take-or-Pay Agreements The company and its subsidiaries have certain contingent liabilities with respect to long-term unconditional purchase obligations and commitments, including throughput and take-or-pay agreements, some of which relate to suppliers’ financing arrangements. The agreements typically provide goods and services, such as pipeline and storage capacity, drilling rigs, utilities, and petroleum products, to be used or sold in the ordinary course of the company’s business. The aggregate approximate amounts of required payments under these various commitments are: 2018 – $1.4 billion; 2019 – $1.4 billion; 2020 – $1.0 billion; 2021 – $0.9 billion; 2022 – $0.5 billion; 2023 and after – $2.6 billion. A portion of these commitments may ultimately be shared with project partners. Total payments under the agreements were approximately $1.3 billion in 2017, $1.3 billion in 2016 and $1.9 billion in 2015.

Direct Guarantees

The company has two guarantees of equity affiliates totaling $1.08 billion. Of this amount, $712 million is associated with a financing arrangement with an equity affiliate. Over the approximate 4-year remaining term of this