In recent years, a rapidly increasing demand for telephone numbers in a competitive environment has required numerous area code splits, overlays, and other number optimization measures.  In this report, we summarize the second systematic collection of comprehensive data on the utilization of telephone numbers within the United States.  The underlying information was acquired from carriers holding numbering resources and analyzed as part of our ongoing assessment of the efficacy of numbering resource optimization measures prescribed by the Commission’s recent NRO Orders.  In general, the reported data show that, of the roughly one billion numbers held by U.S. carriers that reported utilization data on their numbering resources, about 40% are assigned to subscribers and in active use, about 50% are available for use, and the remaining 10% are dedicated to administrative and other purposes. Also, numbering resource utilization rates are rising, and carriers are voluntarily returning millions of numbers so that they can be assigned to other carriers.

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