increased our revenue by \$7 million in 2017, and a 1% increase would have decreased our revenue by\$29 million in 2017.

For additional information about the CAF Phase 2 support program, see “Business—Regulations” in Item 1 of our Annual Report on Form 10-K for the year ended December 31, 2017.

# Income Taxes

Our provision for income taxes includes amounts for tax consequences deferred to future periods. We record deferred income tax assets and liabilities reflecting future tax consequences attributable to tax credit carryforwards, differences between the financial statement carrying value of assets and liabilities and the tax bases of those assets and liabilities and tax net operating loss carryforwards, or NOLs. Deferred taxes are computed using enacted tax rates expected to apply in the year in which the differences are expected to affect taxable income. The effect on deferred income tax assets and liabilities of a change in tax rate is recognized in earnings in the period that includes the enactment date.

The measurement of deferred taxes often involves the exercise of considerablej udgment related to the realization of tax basis. Our deferred tax assets and liabilities reflect our assessment that tax positions taken in filed tax returns and the resulting tax basis are more likely than not to be sustained if they are audited by taxing authorities. Assessing tax rates that we expect to apply and determining the years when the temporary differences are expected to affect taxable income requiresj udgment about the future apportionment of our income among the states in which we operate. Any changes in our practices orj udgments involved in the measurement of deferred tax assets and liabilities could materially impact our financial condition or results of operations.

In connection with recording deferred income tax assets and liabilities, we establish valuation allowances when necessary to reduce deferred income tax assets to amounts that we believe are more likely than not to be realized. We evaluate our deferred tax assets quarterly to determine whether adjustments to our valuation allowance are appropriate in light of changes in facts or circumstances, such as changes in tax law, interactions with taxing authorities and developments in case law. In making this evaluation, we rely on our recent history of pre-tax earnings. We also rely on our forecasts of future earnings and the nature and timing of future deductions and benefits represented by the deferred tax assets, all which involve the exercise of significantj udgment. At December 31, 2017, we established a valuation allowance of \$1.341 billion primarily related to foreign and state NOLs that we acquired from Level 3, as it is more likely than not that these NOLs will expire unused. If forecasts of future earnings and the nature and estimated timing of future deductions and benefits change in the future, we may determine that a valuation allowance for certain deferred tax assets is appropriate, which could materially impact our financial condition or results of operations. See Note 13—Income Taxes to our consolidated financial statements in Item 8 of our Annual Report on Form 10-K for the year ended December 31, 2017 for additional information.

# LIQUIDITY AND CAPITAL RESOURCES

# Overview of Sources and Uses of Cash

We are a holding company that is dependent on the capital resources of our subsidiaries to satisfy our parent company liquidity requirements. Several of our significant operating subsidiaries have borrowed funds either on a standalone basis or as part of a separate restricted group with certain of its subsidiaries or affiliates. The terms of the instruments governing the indebtedness of these borrowers or borrowing groups may restrict our ability to access their accumulated cash. In addition, our ability to access the liquidity of these and other subsidiaries may be limited by tax and legal considerations and other factors.

At December 31, 2017, we held cash and cash equivalents of \$551 million and we had \$1.595 billion of borrowing capacity available under the then existing terms of our revolving credit facility. We had approximately