A rank of 1 is assigned to counties with 810,000+ families. It indicates the county is part of the 20 largest metropolitan areas which together make up 40% of US families.
A rank of 2 is assigned to counties with between 85,000 and 809,999 families. It indicates the county is part of the next largest set of metropolitan areas which together make up 30% of US families.
A rank of 3 is assigned to counties with between 20,000 and 84,999 families. It indicates the county does not meet the criteria for a 1 or 2 rank and either has a population of 20,000+ families or is part of a metropolitan area of 40,000+.
A rank of 4 is assigned to counties with under 20,000 families. It indicates the county does not meet the criteria for a rank of 1, 2, or 3.