ITEM 6. SELECTED FINANCIAL DATA
The following tables of selected consolidated financial data should be read in conjunction with, and are qualified by reference to, our consolidated financial statements and notes thereto in Item 8 of Part II and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in Item 7 of Part II of this report.
The tables of selected financial data shown below are derived from our audited consolidated financial statements, which include the operating results, cash flows and financial condition of Level 3 beginning November 1, 2017. These historical results are not necessarily indicative of results that you can expect for any future period.
The following table summarizes selected financial information from our consolidated statements of operations.
(1) See “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Results of Operations” in Item 7 of Part II of this report and in our preceding annual reports on Form 10-K for a discussion of unusual items affecting the results for each of the years presented.
(2) During 2019 and 2018, we recorded non-cash, non-tax-deductible goodwill impairment charges of $6.5 billion and $2.7 billion, respectively.
(3) During 2019, 2018, 2017 and 2016, we incurred Level 3 acquisition-related expenses of $234 million, $393 million, $271 million and $52 million, respectively. For additional information, see “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Acquisition of Level 3” and Note 2—Acquisition of Level 3 to our consolidated financial statements in Item 8 of Part II of this report.
(4) During 2019, 2018, 2017, 2016 and 2015, we recognized an incremental $157 million, $171 million, $186 million, $201 million and $215 million, respectively, of revenue associated with the Federal Communications Commission (“FCC”) Connect America Fund Phase II support program, as compared to revenue received under the previous interstate USF program.
(5) The enactment of the Tax Cuts and Jobs Act 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 tax expense of $92 million for 2018 and a tax benefit of approximately $1.1 billion for 2017.
Table:
 |  |  | Years Ended December 31,(1) |  | 
 | 2019(2)(3)(4) | 2018(2)(3)(4)(5) | 2017(3)(4)(5) | 2016(3)(4) | 2015(4)
 |  |  | (Dollars in millions, except per share amounts and shares in thousands) |  | 
Operating revenue | $22,401 | 23,443 | 17,656 | 17,470 | 17,900
Operating expenses | 25,127 | 22,873 | 15,647 | 15,137 | 15,321
Operating (loss) income | $(2,726) | 570 | 2,009 | 2,333 | 2,579
(Loss) income before income tax expense | $(4,766) | (1,563) | 540 | 1,020 | 1,316
Net (loss) income | $(5,269) | (1,733) | 1,389 | 626 | 878
Basic loss) earnings per common share | $(4.92) | (1.63) | 2.21 | 1.16 | 1.58
Diluted (loss) earnings per common share | $(4.92) | (1.63) | 2.21 | 1.16 | 1.58
Dividends declared per common share | $1.00 | 2.16 | 2.16 | 2.16 | 2.16
Weighted average basic common shares outstanding | 1,071,441 | 1,065,866 | 627,808 | 539,549 | 554,278
Weighted average diluted common shares outstanding | 1,071,441 | 1,065,866 | 628,693 | 540,679 | 555,093


Question: Which year has the lowest operating expenses?
Answer: 2016
Calculation: $15,137<$15,321<$15,647<$22,873<$25,127