block numbering area
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block numbering area (BNA)
A small, relatively permanent statistical subdivision within a county, generally containing 2,500 to 8,000 people and having readily identifiable borders. Similar to census tracts, but differing only in the local versus federal source of the data used to create the maps.Mapped and numbered by the U.S.government,which provides demographic information at www.census.gov. Third-party resellers of demographic information extrapolate from the census tract data into more personalized demographic areas.