Table
1. Census Statistical Areas
|
Geographic Area
|
Definition |
Number
in 1990 |
Census
tract/
Block numbering area (BNA) |
Census
tracts are small, locally defined statistical areas in metropolitan
areas and densely populated counties. In nonmetropolitan areas,
BNAs are equivalent to census tracts. In Census 2000, the term
"census tract" will replace BNA.
Initially delineated to be homogeneous with
respect to population characteristics, economic status, and
living conditions, census tracts generally have stable boundaries
to facilitate longitudinal population comparisons. Total population
size ranges from 2,500 to 8,000 persons, with an average of
4,000. Area size is determined by settlement density.
Census tract boundaries are linked to census
data in a GIS with a six-digit Federal Information Processing
Standards (FIPS) code.
|
62,276
|
| Block group
(BG)
|
BGs are
groupings of census blocks within census tracts or BNAs. The first
number assigned to each block identifies the block group of which
it is a part. A block group may contain up to 97 blocks, but usually
the number is substantially less. BGs generally contain between
250 and 550 housing units, with an average of 340. |
229,192
|
| Block |
Blocks are
the smallest census geographic area used by the Bureau of the
Census for data tabulation and presentation. Block boundaries
are usually streets and other prominent physical features. Political
divisions can also serve as block boundaries. Blocks may be as
small as a typical city block bounded by four streets or as large
as several square miles in rural areas. The 1990 census is the
first in which the entire country is block-numbered.
Blocks have a three-digit FIPS code (some might
contain a letter at the end of the code). In Census 2000, blocks
will have a four-digit numeric code.
|
7,017,425
|
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This page last updated on
April 17, 2002
Contact Name: Wilma López/ WLópez@cdc.gov
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