Item 6. Selected Financial Data

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The following table sets forth our selected historical consolidated financial information for each of the five years in the period ended December 31, 2017. The statement of operations data, the statement of cash flows data and the other data for the years ended December 31, 2017, 2016 and 2015 and the balance sheet data as of December 31, 2017 and 2016 were derived from our audited consolidated financial statements included elsewhere in this Form 10-K. The statement of operations data, the statement of cash flows data and the other data for the years ended December 31, 2014 and 2013, and the balance sheet data as of December 31, 2015, 2014 and 2013 were derived from our audited consolidated financial statements that are not included in this Form 10-K.

The selected financial data presented below is not necessarily indicative of results of future operations and should be read in conjunction with our consolidated financial statements and the information included under the headings “Management's Discussion and Analysis of Financial Condition and Results of Operations” included elsewhere in this Form 10-K.

Note: We have not declared any cash dividends on common stock for the periods shown.

EBITDA and adjusted EBITDA are not recognized measurements under accounting principles generally accepted in the United States, or GAAP. When analyzing our operating performance, investors should use these measures in addition to, and not as an alternative for, their most directly comparable financial measure calculated and presented in accordance with GAAP. We generally use these non-GAAP financial measures to evaluate operating performance and for other discretionary purposes. We believe these measures provide a more complete understanding of ongoing operations, enhance comparability of current results to prior periods and may be useful for investors to analyze our financial performance because they eliminate the impact of selected charges that may obscure trends in the underlying performance of our business. Because not all companies use identical calculations, our presentation of EBITDA and adjusted EBITDA may not be comparable to similarly titled measures of other companies.

EBITDA represents earnings before net interest expense, write-off of financing costs on extinguished debt, income taxes, depreciation and amortization. Amounts shown for adjusted EBITDA further remove (from EBITDA) the impact of certain cash and non-cash charges related to acquisitions, cost-elimination expenses and certain carried interest incentive compensation expense (reversal) to align with the timing of associated revenue. We believe that investors may find these measures useful in evaluating our operating performance compared to that of other companies in our industry because their calculations generally eliminate the effects of acquisitions, which would include impairment charges of goodwill and intangibles created from acquisitions, the effects of financings and income taxes and the accounting effects of capital spending.

EBITDA and adjusted EBITDA are not intended to be measures of free cash flow for our discretionary use because they do not consider certain cash requirements such as tax and debt service payments. These measures may also differ from the amounts calculated under similarly titled definitions in our debt instruments, which amounts are further adjusted to reflect certain other cash and non-cash charges and are used by us to determine compliance with financial covenants therein and our ability to engage in certain activities, such as incurring additional debt and making certain restricted payments. We also use adjusted EBITDA as a significant component when measuring our operating performance under our employee incentive compensation programs.

EBITDA and adjusted EBITDA are calculated as follows (dollars in thousands):