U.S. Areas of Dominant Influence (ADIs) usually consist of one or more whole counties of the United States, and represent the viewing areas of commercial and satellite television stations that receive the majority of total viewing hours based on annual statistical survey samples. The Arbitron Ratings Company defines the areas. Areas of Dominant Influence are typically named for their major metropolitan area. Some Areas of Dominant Influence have outlying areas with strong secondary influence.
Environmental Systems Research Institute, Inc. (ESRI)