On both mainstream radio and public radio, radio listening is measured by Arbitron and others in the United States. Arbitron and related services have a regional business and regular daytime forecasts but do not collect national host data. Since Arbitron’s coverage in rural areas has substantial gaps, and since there are only a few areas where Arbitron’s proprietary statistics can be measured to rival rating measurers when seeking to assemble a list of the most listened-to radio shows in the United States, there is a great deal of calculation and interpolation.