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ZIP Code Tabulation Area

ZIP Code Tabulation Area

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ZIP Code Tabulation Areas (ZCTAs) are statistical entities developed by the United States Census Bureau
United States Census Bureau
The United States Census Bureau is the government agency that is responsible for the United States Census. It also gathers other national demographic and economic data...

 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
ZIP Code
ZIP codes are a system of postal codes used by the United States Postal Service since 1963. The term ZIP, an acronym for Zone Improvement Plan, is properly written in capital letters and was chosen to suggest that the mail travels more efficiently, and therefore more quickly, when senders use the...

. Defining the extent of an area is necessary in order to tabulate census data for that area.

ZCTAs are generalized area representations of the United States Postal Service
United States Postal Service
The United States Postal Service is an independent agency of the United States government responsible for providing postal service in the United States...

 (USPS) ZIP code service areas, but are not the same as ZIP codes. Individual USPS ZIP codes can cross state
U.S. state
A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

, place, county, census tract
Census tract
A census tract, census area, or census district is a geographic region defined for the purpose of taking a census. Usually these coincide with the limits of cities, towns or other administrative areas and several tracts commonly exist within a county...

, census block group
Census block group
A census block group is a geographical unit used by the United States Census Bureau which is between the census tract and the census block. It is the smallest geographical unit for which the bureau publishes sample data, i.e data which is only collected from a fraction of all households.Census...

 and census block
Census block
A census block is the smallest geographic unit used by the United States Census Bureau for tabulation of 100-percent data . Several blocks make up block groups, which again make up census tracts. There are on average about 39 blocks per block group, but there are variations...

 boundaries, so the Census Bureau asserts that "there is no correlation between ZIP codes and Census Bureau geography." Moreover, the USPS frequently realigns, merges, or splits ZIP codes to meet changing needs. These changes are usually not reflected in the annual TIGER
Topologically Integrated Geographic Encoding and Referencing
Topologically Integrated Geographic Encoding and Referencing, or TIGER, or TIGER/Line is a format used by the United States Census Bureau to describe land attributes such as roads, buildings, rivers, and lakes, as well as areas such as census tracts...

 releases. Each ZCTA is constructed by aggregating the Census 2000 blocks
Census block
A census block is the smallest geographic unit used by the United States Census Bureau for tabulation of 100-percent data . Several blocks make up block groups, which again make up census tracts. There are on average about 39 blocks per block group, but there are variations...

 whose addresses
Address (geography)
An address is a collection of information, presented in a mostly fixed format, used for describing the location of a building, apartment, or other structure or a plot of land, generally using political boundaries and street names as references, along with other identifiers such as house or...

use a given ZIP code. In assembling census statistical units to create ZCTAs, the Census Bureau took the ZIP code used by the majority of addresses in each census unit at the time the data was compiled. As a result, some addresses end up with a ZCTA code that is different from their ZIP code. ZCTAs are not developed for ZIP codes that comprise only a small number of addresses. Several ZCTAs represent ZIPs that no longer exist due to realignment by the USPS.

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