CENSUS GEOGRAPHY: OVERVIEW
Introduction
The Decennial Census provides a picture of the population in the
United States at one point in
time. This includes
demographic, social and economic, as well as housing information.
Demographic characteristics include such things as age, sex,
race and ethnic origin. Social
characteristics are marital status, educational attainment,
family type, citizenship, place of birth
and previous residence.
In addition to the population census, the decennial census also includes
census of housing characteristics (type of housing, age of
stock, amenities). This information is
used for a variety of purposes.
In addition to the Constitutional requirement that the United
States House of Representatives be apportioned on this data,
Census 2000 information will be
used for funding of federal and state governmental programs,
planning, economic development,
and research.
The U.S. Census Bureau has the responsibility for the
collection, tabulation and dissemination of
this statistical data. While data is important, the true
usefulness of this information is realized
when the data is linked to geography. The geography can be legal or political entities such as
governmental units or purely statistical in nature such as
census blocks.
Developing geographic boundaries and tracking change is a large
undertaking. There are many
programs designed to keep it current. Many occur each year and
not just during the Decennial
Census process. Just as the questions asked in the Decennial
Census change census to census,
geographic components also evolve.
Programs
Boundary and Annexation Survey
The Census Bureau conducts a Boundary and Annexation Survey
every year. The purpose is to
maintain the inventory of general-purpose governments and obtain
up-to-date information about
boundaries changes. The BAS consists of two parts:
1. A mailing to
counties to verify the listing of minor civil divisions and incorporated places
within each county and obtain any minor civil division or county
boundary changes, and
2. A mailing to
incorporated places and minor civil divisions (in selected states) to obtain
any
municipal boundary changes.
TIGER Improvement Program
The Topographically Integrated Encoded Referencing System (TIGER)
Program provides all
local governments and regional and metropolitan agencies the
opportunity to assist the Census
Bureau in locating and updating street features, street names,
and address ranges identified as
missing or incorrect in the TIGER database. This information is
needed to link U.S. Postal
Service addresses with the TIGER database.
Census Map Preview
The Census Bureau wants every jurisdiction to have an early
picture of the content in the
TIGER database. For those local jurisdictions that will not
receive maps produced from TIGER
through other programs, the Census Bureau will provide Census
Map Preview map sheets.
Local participants may use these maps to furnish the Census
Bureau with updated street
features and their names.
Census 2000 Redistricting Data Program
This program encompasses the various activities that create the
geography for the tabulation of
redistricting data. During the Block Boundary Suggestion Project
(BBSP), the Census Bureau
offered state redistricting officials the opportunity to
identify features they suggest be held as
census 2000 block boundaries. State redistricting officials
later will submit the boundaries of
voting districts (precincts) and state legislative districts
during the Voting District Project, using
many of the features they provided during the BBSP.
Statistical Area Program
This program enables local participants to delineate, following
Census Bureau guidelines,
statistical areas such as census tracts, block groups, census
designated places and census
county divisions.
Other programs include the update of school district and
Congressional district boundaries by
participating state officials; the update of traffic analysis
zones and assistance in place of work
program by metropolitan planning organizations; and other
American Indian and Alaska Native
Programs.
Local Update of Census Addresses
Local governments were given the opportunity to review the
census address lists to be used in
the mailing/delivering of forms for the 2000 Census.
Participants needed to agree to
confidentiality requirements of the lists. This was a new
program specifically designed to
improve the Master Address File for the 2000 Census. It occurred
in 1998 and 1999. Georgia
funded a statewide effort to assist local governments in this
program. Approximately $1 million
was allocated for address updates with the state's Regional
Development Centers (RDCs)
providing technical assistance and support.
The Geography
Census geography is found in two types: statistical or
political. Statistical boundaries are defined
by the U.S. Census Bureau and serve as building blocks to larger
areas of geography. Political
boundaries are legal geographic areas such as municipalities or
counties. Census data is
available for both statistical and political geographic
levels.
Statistical Geography
Census Blocks
Census blocks are the smallest unit of geography. They have
boundaries of streets, streams or
legal entities. Census blocks are larger in rural areas than in
more densely settled areas.
Census Block Groups
Block groups are made up of census blocks. The minimum
population is 600 and is maximum is
3,000 with an optimum population of 1,500. Block group boundaries
should follow visible and
identifiable features.
Census Tracts
Census tracts are made up of census block groups. The population
of a census tract is a
minimum of 1,500 and a maximum of 8,000. The optimum population
is 4,000. Census tract
boundaries must follow visible and identifiable features.
Each census tract must have at least one block group and may
contain as many as nine block
groups. Block group(s) cover the entire land and inland water
area of a census tract.
Census Designated Places
A Census Designated Place (CDP) is a well-known, closely settled
locality that is not
incorporated. A CDP generally contains a mixture of residential,
commercial and retail areas
and should constitute a community larger than an apartment complex,
a housing subdivision, or
an individual neighborhood. A CDP must have a locally recognized
and commonly used name.
It must comprise a compact and contiguous land area with
visible, identifiable features as
boundaries.
Sandy Springs is an example of a CDP in Georgia.
For the 2000 Census, there is no minimum or maximum population
requirements. However, if
the universe is too small, data will not be available.
Urbanized Area
This is a contiguously built up area with a population of 50,000
or more.
Metropolitan Statistical Area
In previous censuses, Metropolitan Statistical Areas (MSA) were
defined as a county or group
of contiguous counties that included a central city. There was a
high level of integration with the
population nucleus such as commuting to work, etc.
A new configuration is being used for Census 2000. These newly designated Core-Based
Statistical Areas (CBSA) are divided into two primary
categories. Areas will populations of
50,000 or more will be Metropolitan Statistical Areas. Those will populations of 10,000 to
49,999 will be Micropolitan Statistical Areas.
Counties will remain the building blocks for these areas. Urban
areas of 50,000 or more or
settlement clusters of 10,000 or more will be the cores of the
CBSA. Central counties will be
based on the location of the cores. Commuting patterns and
employment ratios will be used to
determine aggregating counties into CBSAs. The standards for inclusion based on
commuting
patterns have been increased since 1990. The percentage of a county's workforce that
commutes to a central county has been raised from15 percent to
25 percent. (For a more
detailed explanation of metropolitan standards see Standards for
Defining Metropolitan and
Micropolitan Areas under the documents listing on SDRCs Census
2000 page).
Political/Legal Geography
Minor Civil Divisions (municipalities or mcds)
Georgia has 534 incorporated municipalities according to Census
2000. Atlanta is the largest
city with a population of 416,474. Four other cities, Athens, Augusta, Columbus and Savannah
have populations of over100,000.
Counties
Georgia has 159 counties, the second highest number of any
state. The great majority of these
counties have fewer than 100,000 people. Only four counties have populations in
excess of
500,000 (Fulton, DeKalb, Cobb and Gwinnett). Another 10 counties have populations of over
100,000. Together these
14 counties contain 4.5 million people, 55 percent of the state's
population.
School Districts
There are 180 school districts in Georgia. In addition to 159 county systems, there are
21
independent city school systems. The Census provides only limited data by school district.
Funding for the processing of this data was provided by the U.S.
Department of Education in
1990. A similar
arrangement is expected with Census 2000.
ZIP Codes
Census data is also available for each of the Postal ZIP Codes
in the U.S. ZIP code data is
especially useful to marketers. However, ZIP Codes do cross
census defined and political/legal
boundaries. That is, one ZIP Code may cover parts of two
different municipalities or two
different census tracts.
Because the boundaries do not line up in all situations, statistical
adjustments are necessary to provide census data at the Zip Code
level.
Legislative Districts
The Census Bureau will make complete Census 2000 data available
by Congressional District.
Data for the Georgia General Assembly Senate and House districts
is only provided as part of
the redistricting summary data file. This limits information to numbers of persons, race, Hispanic
origin, and voting age population. Additional information at the state legislative level must be
specially rebuilt using block level data files for these levels
of geography, a lengthy and involved
process.
Summary
Census data is very valuable to the public, private and
non-profit sectors. It is that link to
geography that makes it useful. Local governments have the most
expertise when it comes to
knowing changes in their jurisdictions, whether it is new
housing units or roads. Their input into
the various Census Programs is essential to having a successful
Census and reliable data to use
after the Census is complete.