In the United States, radio listenership is gauged by Nielsen and others for both commercial radio and public radio. Nielsen and similar services provide estimates by regional market and by standard daypart, but do not compile nationwide information by host. Because there are significant gaps in Nielsen's coverage in rural areas, and because there are only a few markets where the company's proprietary data can be compared against competing ratings tabulators, there is a great deal of estimation and interpolation when attempting to compile a list of the most-listened-to radio programs in the United States. In 2009, Arbitron, the American radio industry's largest audience-measurement company at the time (since subsumed into its television counterpart Nielsen), said that "the job of determini