We believe that the network technology migration we have seen in the United States, which has led to significantly denser networks and meaningful new business commencements for us over a number of years, will ultimately be replicated in our less advanced international markets. As a result, we expect to be able to leverage our extensive international portfolio of approximately 108,635 communications sites and the relationships we have built with our carrier tenants to drive sustainable, long-term growth.
We have master lease agreements with certain of our tenants that provide for consistent, long-term revenue and reduce the likelihood of churn. Certain of those master lease agreements are holistic in nature and further build and augment strong strategic partnerships with our tenants and have significantly reduced colocation cycle times, thereby providing our tenants with the ability to rapidly and efficiently deploy equipment on our sites.
Property Operations Expenses. Direct operating expenses incurred by our property segments include direct site level expenses and consist primarily of ground rent and power and fuel costs, some or all of which may be passed through to our tenants, as well as property taxes, repairs and maintenance. These segment direct operating expenses exclude all segment and corporate selling, general, administrative and development expenses, which are aggregated into one line item entitled Selling, general, administrative and development expense in our consolidated statements of operations. In general, our property segments’ selling, general, administrative and development expenses do not significantly increase as a result of adding incremental tenants to our sites and typically increase only modestly year-over-year. As a result, leasing additional space to new tenants on our sites provides significant incremental cash flow. We may, however, incur additional segment selling, general, administrative and development expenses as we increase our presence in our existing markets or expand into new markets. Our profit margin growth is therefore positively impacted by the addition of new tenants to our sites but can be temporarily diluted by our development activities.
Services Segment Revenue Growth. As we continue to focus on growing our property operations, we anticipate that our services revenue will continue to represent a small percentage of our total revenues.
Non-GAAP Financial Measures
Included in our analysis of our results of operations are discussions regarding earnings before interest, taxes, depreciation, amortization and accretion, as adjusted (“Adjusted EBITDA”), Funds From Operations, as defined by the National Association of Real Estate Investment Trusts (“NAREIT FFO”) attributable to American Tower Corporation common stockholders, Consolidated Adjusted Funds From Operations (“Consolidated AFFO”) and AFFO attributable to American Tower Corporation common stockholders.
We define Adjusted EBITDA as Net income before Income (loss) from equity method investments; Income tax benefit (provision); Other income (expense); Gain (loss) on retirement of long-term obligations; Interest expense; Interest income; Other operating income (expense); Depreciation, amortization and accretion; and stock-based compensation expense.
NAREIT FFO attributable to American Tower Corporation common stockholders is defined as net income before gains or losses from the sale or disposal of real estate, real estate related impairment charges, real estate related depreciation, amortization and accretion and dividends on preferred stock, and including adjustments for (i) unconsolidated affiliates and (ii) noncontrolling interests. In this section, we refer to NAREIT FFO attributable to American Tower Corporation common stockholders as “NAREIT FFO (common stockholders).”
We define Consolidated AFFO as NAREIT FFO (common stockholders) before (i) straight-line revenue and expense; (ii) stock-based compensation expense; (iii) the deferred portion of income tax; (iv) non-real estate related depreciation, amortization and accretion; (v) amortization of deferred financing costs, capitalized interest, debt discounts and premiums and long-term deferred interest charges; (vi) other income (expense); (vii) gain (loss) on retirement of long-term obligations; (viii) other operating income (expense); and adjustments for (ix) unconsolidated affiliates and (x) noncontrolling interests, less cash payments related to capital improvements and cash payments related to corporate capital expenditures.
We define AFFO attributable to American Tower Corporation common stockholders as Consolidated AFFO, excluding the impact of noncontrolling interests on both NAREIT FFO (common stockholders) and the other