Area of Dominant Influence

Area of dominant influence, or ADI, is a term used in the advertising and media industries to identify, define, and measure geographic markets in the United States. It is particularly important for sports teams and the television or radio outlets that carry their games, as the revenue earned from selling commercial time is based largely on the size of their ADI.

As used by Arbitron, the audience research company that first coined the term, a market's area of dominant influence includes all those counties from which a central city's broadcast stations receive majority viewership. Since a county can only be included as part of one ADI, in some cases the stations from neighboring markets will compete vigorously to achieve majority status among the viewers in border areas, thus increasing the size of their ADI, enabling them to charge higher advertising rates and increase profits. An example of such a situation is the region of Maryland located between Baltimore and Washington, D.C., where the Baltimore Orioles and their media partners compete with the Washington Nationals and the media that carry them to claim those counties where both teams may have viewership as part of their own area of dominant influence.

While area of dominant influence has long been the accepted market measure for radio, in television, the term designated market area (DMA) is sometimes substituted. Nielsen Media Research, a competitor of Arbitron, employs the DMA label for TV markets but uses essentially the same definition and measures that ADI is based on.

Because of differences in population density and population distribution in various regions of the United States, the geographic size and shape of ADIs is not uniform. Thus, in the urban east, while the areas of dominant influence for important sports cities like New York, Philadelphia, and Boston rank among the very largest in terms of the number of people included, they cover much smaller land areas than most western sports cities, such as Denver, Phoenix, and Salt Lake City. Beyond the business and media implications related to ADI numbers, such geographic dispersion probably explains much about the location and characteristics of the “home fans” for professional and college teams in different parts of the country.

Areas of dominant influence are reevaluated regularly, with counties sometimes being shifted from one ADI to another, ADI size and ranking moving up or down, and new central city ADIs occasionally [Page 70]being created. In 2010, the total number of ADIs in the United States was just under 300. Major American professional sports leagues are concentrated in the largest 50 ADIs, with Milwaukee being the smallest Major League Baseball market (37th largest), Memphis the smallest ADI in the NBA (50th), Buffalo the smallest stateside NHL market (52nd), and Green Bay the smallest NFL market (the combined Green Bay/Appleton ADI ranks 70th).

Even though the most attention, the biggest money, and the most competitive media strategies tend to involve major professional sports league areas of dominant influence, ADI concepts and practices are quite important at other levels as well. Minor league markets, college teams and athletic conferences, and even those high schools whose games are broadcast are impacted in financial and other ways by considerations of how the audience they reach is measured and defined.

...