We utilize certain financial measures that are not calculated in accordance with accounting principles generally accepted in the United States, or GAAP, to assess our financial performance. A non-GAAP financial measure is defined as a numerical measure of a company's financial performance that (i) excludes amounts, or is subject to adjustments that have the effect of excluding amounts, that are included in the comparable measure calculated and presented in accordance with GAAP in the statement of income or statement of cash flows; or (ii) includes amounts, or is subject to adjustments that have the effect of including amounts, that are excluded from the comparable measure so calculated and presented. Our method of computation may or may not be comparable to other similarly titled measures of other companies. The following tables reconcile our non-GAAP financial measures included in our 2003 annual stockholders' report with our financial statements presented in accordance with GAAP.

The table above reconciles Adjusted EBITDA with what management believes is the most directly comparable GAAP measure of liquidity, cash provided by operating activities. Adjusted EBITDA can also be calculated as net loss plus net interest expense, income taxes, depreciation and asset disposal and amortization adjusted for other expense (which was exclusively non-cash), non-cash compensation and debt extinguishment costs (which were not indicative of our on-going cash flows from operations). We believe Adjusted EBITDA provides a meaningful measure of liquidity, providing additional information on our cash earnings from on-going operations, our ability to service our long-term debt and other fixed obligations and our ability to fund continued growth with internally generated funds. Adjusted EBITDA also is considered by many financial analysts to be a meaningful indicator of an entity's ability to meet its future financial obligations. Adjusted EBITDA should not be construed as an alternative to cash flows from operating activities as determined in accordance with GAAP.

We believe ARPU, which calculates the average service revenue billed to an individual subscriber, is a useful measure to evaluate our past billable service revenue and to assist in forecasting our future billable service revenue. ARPU is exclusive of service revenue credits made to retain existing subscribers, as these are discretionary reductions of the amount billed to a subscriber. We have no contractual obligation to issue these credits, therefore, ARPU reflects the amount subscribers have contractually agreed to pay us based on their specific usage pattern. ARPU is calculated by dividing service revenue, exclusive of service revenue credits made to existing subscribers, by our average subscriber base for the respective period. For quarterly periods, average subscribers is calculated by adding subscribers at the beginning of the quarter to subscribers at the end of the end of the quarter and dividing by two; for year-to-date periods, average subscribers is calculated by adding the average subscriber amount calculated for the quarterly periods during the period and dividing by the number of quarters in the period.