This is the Federal Communications Commission’s (FCC’s) report on numbering resource utilization in the United States.  In this report, we summarize the  fourth systematic collection of comprehensive data on the utilization of telephone numbers within the United States.  The underlying information was acquired from carriers ho lding numbering resources and analyzed as part of our ongoing assessment of the efficacy of numbering resource optimization measures prescribed by the Commission’s recent Numbering Resource Optimization (NRO) Orders.