DEFINITION of 'ABCD Counties'
Categories of U.S. counties devised by AC Nielsen Company that are based on U.S. Census Bureau population data and proximity to major metropolitan areas. A counties are the largest U.S. counties by population, and D counties are the smallest. Counties are classified on the basis of data from the latest census, which takes place every 10 years. The county classification is used by marketing and advertising agencies, and advertisers in the preparation and analysis of advertising and media plans.
BREAKING DOWN 'ABCD Counties'
A counties are classified as any county located in the 25 largest U.S. metropolitan areas, which will be the highest density. B counties are considered any county that is not an A county and has a population exceeding 150,000 or is part of a metropolitan area with a population over 150,000. C counties are seen as any county that is not classified as an A or B county, and has a population between 40,000 and 150,000. D counties are any county that not classified as an A, B or C county.