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Vol. 3 - No. 18 Sept. 27, 1999
One of the lesser known new features of Census 2000 data tabulation is
the planned use, for the first time, of ZIP Code Tabulation Areas (TM)
(ZCTAs), a statistical entity developed by the Census Bureau as an
approximation of the U. S. Postal Service's ZIP (R) Codes.
ZIP Codes do not represent areas, but rather a network for the delivery
of mail. The Census Bureau has released prototype ZCTAs for the three
Census 2000 Dress Rehearsal sites (Columbia, S.C., and 11 surrounding
counties; Menominee County, Wis.; and Sacramento, Calif.).
Thus, the ZCTA will take its place alongside standard statistical
tabulation areas, such as regions, divisions, metropolitan areas,
urbanized areas, tribal statistical areas, county subdivisions, census
designated places, census tracts, block groups and census blocks, as
well as the legal and administrative areas for which the Census Bureau
traditionally publishes summary data.
The ZCTAs will be assigned in a computer-delineated process based on the
Census Bureau's address list at the time of the census. The Census
Bureau's address list itself is confidential under Title 13, U.S. Code,
and therefore is not available to the public. ZCTAs follow census block
boundaries, with the ZCTA code for each census block being the majority
ZIP Code for addresses within that census block. Automated processes
will extend ZCTA codes to blocks that have no addresses or no addresses
with ZIP Codes. This means that the Census Bureau will be able to
display the ZCTAs as polygons on maps.
For the Census 2000 Dress Rehearsal sites, ZCTA codes are assigned to
all land -- even that which is uninhabited -- and water areas, which
will be displayed with three-digit instead of five-digit codes. A
three-digit code indicates that the Census Bureau was not confident with
the assignment of a five-digit code based on information available in
its files.
The Census Bureau hopes data users will look at its implementation of
ZCTAs for the Census 2000 Dress Rehearsal sites and provide comments on
the resulting product. More information is available on the Internet at
http://www.census.gov/geo/ZCTA/zcta.html.
ZCTAs exclude unique, single-delivery-point ZIP codes for firms and
organizations, but do include dedicated Post Office Box ZIP Codes where
a main post office has only Post Office Box deliveries.
ZCTAs will be summary levels in both the 100 percent and sample data
files and should be available at the same time as the data for the other
summary levels, between June of 2001 and December of 2002. The Census
Bureau's new American Community Survey plans to tabulate data for ZIP
code tabulation areas once the 2000 ZCTAs become available.
(ZCTA is a trademark of the U. S. Bureau of the Census. ZIP is a
registered trademark of the U. S. Postal Service.)