Certain amounts have been conformed to the current period's presentation, including our adoption of new accounting standards; ASU No. 2017-07, "Compensation – Retirement Benefits (Topic 715): Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost," ASU No. 2016-15, "Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments," and ASU No. 2016-18, Statement of Cash Flows (Topic 230): Restricted Cash; and our realignment of certain responsibilities and operations within our segments, the most significant of which is to report wireless accounts with employer discounts in our Consumer Mobility segment.

Free cash flow is defined as cash from operations minus Capital expenditures. Free cash flow after dividends is defined as cash from operations minus Capital expenditures and dividends. Free cash flow dividend payout ratio is defined as the percentage of dividends paid to free cash flow. We believe these metrics provide useful information to our investors because management views free cash flow as an important indicator of how much cash is generated by routine business operations, including Capital expenditures, and makes decisions based on it. Management also views free cash flow as a measure of cash available to pay debt and return cash to shareowners.

Our calculation of EBITDA, as presented, may differ from similarly titled measures reported by other companies. For AT&T, EBITDA excludes other income (expense) – net, and equity in net income (loss) of affiliates, as these do not reflect the operating results of our subscriber base or operations that are not under our control. Equity in net income (loss) of affiliates represents the proportionate share of the net income (loss) of affiliates in which we exercise significant influence, but do not control. Because we do not control these entities, management excludes these results when evaluating the performance of our primary operations. EBITDA also excludes interest expense and the provision for income taxes. Excluding these items eliminates the expenses associated with our capital and tax structures. Finally, EBITDA excludes depreciation and amortization in order to eliminate the impact of capital investments. EBITDA does not give effect to cash used for debt service requirements and thus does not reflect available funds for distributions, reinvestment or other discretionary uses. EBITDA is not presented as an alternative measure of operating results or cash flows from operations, as determined in accordance with U.S. generally accepted accounting principles (GAAP).

EBITDA service margin is calculated as EBITDA divided by service revenues.

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When discussing our segment results, EBITDA excludes equity in net income (loss) of affiliates, and depreciation and amortization from segment contribution. For our supplemental presentation of our combined domestic wireless operations (AT&T Mobility) and our supplemental presentation of the Mexico Wireless and Latin America operations of our International segment, EBITDA excludes depreciation and amortization from operating income.

These measures are used by management as a gauge of our success in acquiring, retaining and servicing subscribers because we believe these measures reflect AT&T's ability to generate and grow subscriber revenues while providing a high level of customer service in a cost-effective manner. Management also uses these measures as a method of comparing segment performance with that of many of its competitors. The financial and operating metrics which affect EBITDA include the key revenue and expense drivers for which segment managers are responsible and upon which we evaluate their performance. Management uses Mexico Wireless EBITDA in evaluating profitability trends after our two Mexico wireless acquisitions in 2015, and our investments in building a nationwide LTE network by end of 2018. Management uses Latin America EBITDA in evaluating the ability of our Latin America operations to generate cash to finance its own operations.

We believe EBITDA Service Margin (EBITDA as a percentage of service revenues) to be a more relevant measure than EBITDA Margin (EBITDA as a percentage of total revenue) for our Consumer Mobility segment operating margin and our supplemental AT&T Mobility operating margin. We also use wireless service revenues to calculate margin to facilitate comparison, both internally and externally with our wireless competitors, as they calculate their margins using wireless service revenues as well.

There are material limitations to using these non-GAAP financial measures. EBITDA, EBITDA margin and EBITDA service margin, as we have defined them, may not be comparable to similarly titled measures reported by other companies. Furthermore, these performance measures do not take into account certain significant items, including depreciation and amortization, interest expense, tax expense and equity in net income (loss) of affiliates. Management compensates for these limitations by carefully analyzing how its competitors present performance measures that are similar in nature to EBITDA as we present it, and considering the economic effect of the excluded expense items independently as well as in connection with its analysis of net income as calculated in accordance with GAAP. EBITDA, EBITDA margin and EBITDA service margin should be considered in addition to, but not as a substitute for, other measures of financial performance reported in accordance with GAAP.

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Adjusting items include revenues and costs we consider nonoperational in nature, such as items arising from asset acquisitions or dispositions. We also adjust for net actuarial gains or losses associated with our pension and postemployment benefit plans due to the often significant impact on our fourth-quarter results, unless earlier remeasurement is required (we immediately recognize this gain or loss in the income statement, pursuant to our accounting policy for the recognition of actuarial gains and losses.) Consequently, our adjusted results reflect an expected return on plan assets rather than the actual return on plan assets, as included in the GAAP measure of income.

Adjusted Operating Income, Adjusted Operating Income Margin, Adjusted EBITDA, Adjusted EBITDA margin, Adjusted EBITDA service margin and Adjusted diluted EPS are non-GAAP financial measures calculated by excluding from operating revenues, operating expenses and income tax expense certain significant items that are non-operational or non-recurring in nature, including dispositions and merger integration and transaction costs. Management believes that these measures provide relevant and useful information to investors and other users of our financial data in evaluating the effectiveness of our operations and underlying business trends.

Adjusted Operating Revenues, Adjusted Operating Income, Adjusted Operating Income Margin, Adjusted EBITDA, Adjusted EBITDA margin, Adjusted EBITDA service margin and Adjusted diluted EPS should be considered in addition to, but not as a substitute for, other measures of financial performance reported in accordance with GAAP. AT&T's calculation of Adjusted items, as presented, may differ from similarly titled measures reported by other companies.

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Net Debt to EBITDA ratios are non-GAAP financial measures frequently used by investors and credit rating agencies and management believes these measures provide relevant and useful information to investors and other users of our financial data. Our Net Debt to Pro Forma Adjusted EBITDA ratio is calculated by dividing the Net Debt by Annualized Pro Forma Adjusted EBITDA. Net Debt is calculated by subtracting cash and cash equivalents and certificates of deposit and time deposits that are greater than 90 days, from the sum of debt maturing within one year and long-term debt. Annualized Pro Forma Adjusted EBITDA is calculated by annualizing the year-to-date Pro Forma Adjusted EBITDA.

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We provide a supplemental discussion of our domestic wireless operations that is calculated by combining our Consumer Mobility and Business Solutions segments, and then adjusting to remove non-wireless operations. The following table presents a reconciliation of our supplemental AT&T Mobility results.

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We provide a supplemental presentation of the Mexico Wireless and Latin America operations within our International segment. The following table presents a reconciliation of our International segment.