ZIP Code Tabulation Area
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ZIP Code Tabulation Areas (ZCTAs™) are a new statistical entity developed by the United States Census Bureau for tabulating summary statistics from Census 2000. This new entity was developed to overcome the difficulties in precisely defining the land area covered by each ZIP Code. Defining the extent of an area is necessary in order to accurately tabulate census data for that area.
ZCTAs are generalized area representations of United States Postal Service (USPS) ZIP Code service areas. Simply put, each one is built by aggregating the Census 2000 blocks, whose addresses use a given ZIP Code, into a ZCTA which gets that ZIP Code assigned as its ZCTA code. They represent the majority USPS five-digit ZIP Code found in a given area.