amount of net premium amortization recorded at acquisition due to the early retirement of several issuances of debt during the period, which has the effect of increasing interest expense, and an increase in interest expense on unsecured notes related to the issuance of \$1.0 billion of new debt in April, 2016 in advance of a debt maturity in June, 2016.

# Other Income, Net

Other income, net reflects certain items not directly related to our core operations, including our share of income from partnerships we do not control, interest income, gains and losses from non-operating asset dispositions, foreign currency gains and losses and components of net periodic pension and postretirement benefit costs. Other income (expense), net increased by \$7 million, or 140%, for the year ended December 31, 2017 as compared to the year ended December 31, 2016. This increase in other income, net was primarily due to a reduction in the loss on early retirement of debt, an increase in interest income from the \$6 billion Term Loan B funds held in escrow and income generated from our services agreements with Cyxtera, which was substantially offset by a lower expected return on assets in 2017 for our pension and post-retirement plans. The expected return on assets for our pension and post-retirement plans was lower in 2017 as compared to 2016, which resulted in us recording pension and post-retirement expense in 2017 as compared to recording pension and post-retirement income in 2016. Other income, net decreased by \$44 million, or 90%, for the year ended December 31, 2016 as compared to the year ended December 31, 2015. This decrease in other income, net was primarily due to losses on early retirement of debt, which was partially offset by the impact of nonrecurring funding from a state economic development program.

# Income Tax (Benefits) Expense

The enactment of the Tax Cuts and Jobs Act legislation in December 2017 resulted in a re-measurement of our deferred tax assets and liabilities at the new federal corporate tax rate of 21%. The re-measurement resulted in a tax benefit of approximately \$1.1 billion recorded in the fourth quarter of 2017, which was the predominant factor contributing to our recognition of an \$849 million income tax benefit for 2017, versus income tax expense of \$394 million in the prior year. Income tax expense decreased by \$44 million for the year ended December 31, 2016 as compared to the year ended December 31, 2015. For the years ended December 31, 2017, 2016 and 2015, our effective income tax rate was (157.2)%, 38.6% and 33.3%, respectively. The effective tax rate for the year ended December 31, 2017 reflects the benefit from the re-measurement of deferred taxes as noted above, a\$27 million tax expense related to the sale of our data centers and colocation business and a \$32 million tax impact of non-deductible transaction costs related to the Level 3 acquisition. The effective tax rate for the year ended December 31, 2016 reflects a tax impact of \$18 million from an intercompany dividend payment from one of our foreign subsidiaries to its domestic parent company that was made as part of our corporate restructuring in preparation for the sale of our colocation business. The effective tax rate for the year ended December 31, 2015 reflects a tax benefit of approximately \$34 million related to affiliate debt rationalization, research and development tax credits of \$28 million for 2011 through 2015, and a \$16 million tax decrease due to changes in state taxes caused by apportionment changes, state tax rate changes and the changes in the expected utilization of net operating loss carryforwards (“NOLs”). 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 and “Critical Accounting Policies and Estimates—Income Taxes” below for additional information.