Item 6. SELECTED FINANCIAL DATA

The following tables present our selected consolidated financial data as of and for the dates and periods indicated. We derived the financial data set forth below for 2020, 2019 and 2018 and as of December 31, 2020 and 2019 from our audited consolidated financial statements, which are included in this Annual Report. We derived the financial data for 2017 and 2016 and as of December 31, 2018, 2017 and 2016 from our audited consolidated financial statements, which are not included in this Annual Report. The selected consolidated financial data presented below is not indicative of our future results for any period. It should be read in conjunction with our consolidated financial statements and related notes and Item 7, “- Management’s Discussion and Analysis of Financial Condition and Results of Operations” included in this Annual Report.

(1) Our revenues include transaction and clearing fees within our exchanges and fixed income and data services segments. Such transaction and clearing fees are presented net of rebates paid to our customers.

(2) Our exchanges segment also includes transaction-based expenses relating to Section 31 fees and payments made for routing services and to certain U.S. equities liquidity providers. For a discussion of these rebates, see Item 7 “- Management’s Discussion and Analysis of Financial Condition and Results of Operations - Segment Reporting - Exchanges Segment” included in this Annual Report.

(3) Acquisition-related transaction and integration costs include fees for investment banking advisors, lawyers, accountants, tax advisors and public relations firms, as well as costs associated with credit facilities, debt securities and other external costs directly related to acquisitions and other strategic opportunities. We incurred integration costs during 2020 relating to our Ellie Mae acquisition, and in 2018, 2017 and 2016 relating to our Interactive Data acquisition. Acquisition-related transaction and integration costs during 2016 also include costs related to our NYSE integration. Costs related to Ellie Mae, Interactive Data and NYSE primarily include employee termination costs, lease termination costs and professional services costs relating to the integrations.

(4) Other income (expense), net during 2020 includes $357 million in interest expense, which increased $72 million from 2019 due to the issuance of new senior notes in May 2020 and August 2020, including $5 million in pre-acquisition interest expense related to the notes issued in August 2020 in connection with the Ellie Mae acquisition, as well as a $14 million extinguishment payment we incurred related to the June 2020 early redemption of senior notes with an original maturity of December 1, 2020. It also includes gains of $35 million and $20 million on our Euroclear and BIDS investments, respectively, and an accrual for potential legal settlements of $30 million. Other income (expense), net during 2019 includes a $16 million impairment on promissory notes, interest expense of $285 million and interest income of $35 million. Other income (expense), net during 2018 includes a $110 million gain on our initial investment value in MERS recorded on October 3, 2018, the date we completed our acquisition, interest expense of $244 million and interest income of $22 million. Other income (expense), net during 2017 includes a $167 million realized net investment gain in connection with our sale of Cetip and a $110 million net gain on our divestiture of Trayport, interest expense of $187 million and interest income of $8 million. Refer to Notes 3, 4 and 10 to our consolidated financial statements and related notes, which are included in this Annual Report, for more information.

(5) The income tax benefit in 2017 is primarily due to the $764 million deferred tax benefit associated with U.S. income tax rate reductions enacted in 2017.

(6) The weighted average common shares outstanding decreased in 2020 from 2019 primarily due to stock repurchases, partially offset by the approximately 18.4 million shares of our common stock issued in connection with the Ellie Mae acquisition. The weighted average common shares outstanding decreased in 2019 and 2018 compared to 2018 and 2017, respectively, primarily due to our share repurchases. In 2016 we issued 32.3 million and 12.6 million shares of our common stock to Interactive Data and Trayport stockholders, as part of those acquisitions, respectively.

(1) Clearing members of our clearing houses are required to deposit original margin and variation margin and, for our clearing houses other than ICE NGX, to make deposits to a guaranty fund. The cash deposits made to these margin accounts and to the guaranty fund are recorded in the consolidated balance sheet as current assets with corresponding current liabilities to the clearing members that deposited them. We also account for the physical delivery of our energy contracts for ICE NGX following its acquisition in December 2017. Refer to Note 14 to our consolidated financial statements, included in this Annual Report, for more information on these items.