ABSTRACT
In the decades when television was a new medium, viewing it was an event and an experience in itself. But now viewers are very familiar with the medium, and television is available twenty-four hours a day and is provided on numerous channels delivered by conventional terrestrial broadcasting, through cable and satellite transmission and increasingly through interactive digital services. These increases in the quantity of television and the choices of what to view have made it increasingly difficult for broadcasters to gain reliable information about what audiences watch. This chapter discusses the largely numerical means by which broadcasters gain information about audience sizes, and why this information is important to them.
