Radio stations today generally run their advertising in clusters or sets, scattered throughout the broadcasting hour. Studies show that the first or second commercial to air during a commercial break has higher recall than those airing later in the set.
Arbitron is one of the primary providers of ratings data in the United States. Most radio stations and advertising agencies subscribe to this paid service, because ratings are key in the broadcast industry. Ad agencies generally purchase radio based on a target demographic. For example, their client may want to reach men between 18 and 49 years old. The ratings enable advertisers to select a specific segment of the listening audience and purchase airtime accordingly. Ratings are also referred to as “numbers” in the business.[2