ARPU increased primarily due to the increase in certain of our subscription rates beginning in January 2012, an increase in sales of premium services, including Premier packages, data services and streaming, partially offset by an increase in subscriber retention programs and in the number of subscribers on promotional plans and a decrease in the revenue from the U.S. Music Royalty Fee due to the December 2010 reduction in the rate from 15.3% to 10.8%.

          SAC, Per Gross Subscriber Addition, increased in the three months ended March 31, 2012 primarily due to higher subsidies related to increased OEM installations occurring in advance of acquiring the subscriber, partially offset by improved OEM subsidy rates per vehicle compared to the three months ended March 31, 2011.

Glossary

Adjusted EBITDA- EBITDA is defined as net income before interest and investment loss; interest expense, net of amounts capitalized; income tax expense and depreciation and amortization. We adjust EBITDA to remove the impact of other income and expense, loss on extinguishment of debt as well as certain other charges discussed below. This measure is one of the primary Non-GAAP financial measures on which we (i) evaluate the performance of our businesses, (ii) base our internal budgets and (iii) compensate management. Adjusted EBITDA is a Non-GAAP financial performance measure that excludes (if applicable): (i) certain adjustments as a result of the purchase price accounting for the Merger, (ii) goodwill impairment, (iii) restructuring, impairments, and related costs, (iv) depreciation and amortization and (v) share-based payment expense. The purchase price accounting adjustments include: (i) the elimination of deferred revenue associated with the investment in XM Canada, (ii) recognition of deferred subscriber revenues not recognized in purchase price accounting, and (iii) elimination of the benefit of deferred credits on executory contracts, which are primarily attributable to third party arrangements with an OEM and certain programming providers. We believe adjusted EBITDA is a useful measure of the underlying trend of our operating performance, which provides useful information about our business apart from the costs associated with our physical plant, capital structure and purchase price accounting. We believe investors find this Non-GAAP financial measure useful when analyzing our results and comparing our operating performance to the performance of other communications, entertainment and media companies. We believe investors use current and projected adjusted EBITDA to estimate our current and prospective enterprise value and to make investment decisions. Because we fund and build-out our satellite radio system through the periodic raising and expenditure of large amounts of capital, our results of operations reflect significant charges for depreciation expense. The exclusion of depreciation and amortization expense is useful given significant variation in depreciation and amortization expense that can result from the potential variations in estimated useful lives, all of which can vary widely across different industries or among companies within the same industry. We believe the exclusion of restructuring, impairments and related costs is useful given the nature of these expenses. We also believe the exclusion of share-based payment expense is useful given the significant variation in expense that can result from changes in the fair value as determined using