Percept Data Sources: Census

DO YOU REPRESENT. . . A CHURCH? | A REGIONAL AGENCY? | A NATIONAL AGENCY?


	The US Census

The foundation of all demographic information about people is the national Census. The decennial Census was established in 1790 to provide population counts for apportioning seats in the U.S. House of Representatives. The 2000 Census represents the 22nd consecutive decennial Census, and is the most sophisticated and comprehensive census in history. In addition to determining each state’s congressional representation, the Census is used to redefine the boundaries state for congressional districts. The Census also provides the basis for funding and execution of federal programs, such as unemployment insurance, low-income housing, energy and child assistance. Many businesses, state and local governments, universities, as well as churches and human service organizations, depend on the Census to provide a solid and reliable foundation for understanding people and communities in the United States.

There are two questionnaires from which the Census Bureau derives its data—a short form and a long form. The short form was sent to every household, and the long form, containing the 100 percent questions plus the sample questions, was sent to only a limited number of households. The categories of questions are summarized below:

100-Percent Component

Household Relationship
Sex
Age
Hispanic or Latino Origin
Race
Tenure (owned or rented)

Sample Component

Population

Social Characteristics

Marital status

Place of birth, citizenship,
and year of entry

School enrollment and educational attainment

Ancestry

Residence 5 years ago (Migration)

Language spoken at home

Veteran status

Disability

Grandparents as caregivers

Labor Force Status

Labor force status

Place of work and journey to work

Occupation, industry,
and class of worker

Work status in 1999

Income in 1999

Housing

Physical Characteristics

Units in structure

Year structure built

Number of rooms and
number of bedrooms

Year moved into residence

Plumbing and kitchen facilities

Telephone service

Vehicles available

Heating fuel

Farm residence

Financial Characteristics

Value of home or
monthly rent paid

Utilities, mortgage, taxes, insurance, and fuel costs

Generally, about one in every six houses nationwide received the long form. The rate varied from one in two households in some smaller areas, to one in eight households for more densely populated areas.

Estimates from the Census sample were obtained from a ratio estimation procedure resulting in the assignment of a weight to each sample person or housing unit record. For any given tabulation area, a characteristic total was estimated by summing the weights assigned to the persons or housing units possessing the characteristic in the tabulation process.

Population totals for the same tract can differ depending on the source questionnaire. On the sample questionnaire, if a census tract has fewer than 400 sample cases, it is normally combined with another tract to make up a sample-weighted area. As a result, the sample count (Summary Tape File 3) and 100-percent count (Summary Tape File 1) totals will not match exactly for
either tract, but should match if the tracts are counted together. Specifically, the tract with less than 400 cases is combined with another tract having a code (tract number) nearest its own within the jurisdiction, regardless of geographic proximity. Sample and
100-percent populations will match at the county, place or minor civil division (active) level.

The Census Bureau provides demographic data and TIGER (Topologically Integrated Geographic Encoding and Referencing) files for numerous census and political geographies. The Census Bureau classifies all geographic entities into two broad categories: legal and administrative entities, and statistical entities.

Legal and Administrative Entities

The Primary Group of geographies forms a hierarchy that provides the foundation for many applications. These geographies are non-overlapping in hierarchy:

Congressional District

County

Incorporated Place (cities, towns, villages, etc.)

Minor Civil Division (MCD)

State

United States

Voting District (VTD)

Legal/Administrative entities generally originate from charters, laws, treaties, resolutions, or court decisions. They include:

Congressional District. One of the 435 areas from which people are elected to the U.S. House of Representatives.

County. The primary legal division of every state except Alaska and Louisiana. A number of geographic entities are not legally designated as a county, but are recognized by the Census Bureau as equivalent to a county for data presentation purposes. These include the boroughs, city and boroughs, municipalities, and census areas in Alaska; parishes in Louisiana; and cities that are independent of any county in Maryland, Missouri, Nevada, and Virginia. They also include the municipios in Puerto Rico, districts and islands in American Samoa, municipalities in the Northern Mariana Islands, and islands in the Virgin Islands of the United States. Because they contain no primary legal divisions, the Census Bureau treats the District of Columbia and Guam each as equivalent to a county (as well as equivalent to a state) for data presentation purposes. In American Samoa, a county is a minor civil division.

Incorporated Place (cities, towns, villages, etc.). A type of governmental unit, incorporated under state law as a city, town (except in New England, New York, and Wisconsin), borough (except in Alaska and New York), or village, generally to provide a wide array of specific governmental services for a concentration of people within legally prescribed boundaries. New for Census
2000 are “city and borough ” and “municipality,” which serve as both place- and county-level entities in Alaska.

Minor Civil Division (MCD). The primary governmental or
administrative division of a county or statistically equivalent entity in many states and statistically equivalent entities. MCDs are identified by a variety of terms, such as township, town (in 8 states), or district. The Census Bureau recognizes MCDs in 28 states, the District of Columbia, Puerto Rico, and the Island Areas. In 20 states and American Samoa, all or many MCDs are
active general-purpose governmental units. Many MCDs are not general-purpose governmental units, and therefore do not have elected officials to carry out legal functions; instead, they serve as nonfunctioning administrative entities.

State. A primary governmental division of the United States. The Census Bureau treats the District of Columbia as the equivalent of a state for data presentation purposes. It also treats a number of entities that are not legal divisions of the United States (e.g. Island Areas) as the equivalent of states for data presentation purposes.

United States. The 50 states and the District of Columbia.

Voting District (VTD). The generic name for a geographic entity—such as an election district, precinct, or ward—established by state, local, and tribal governments for the purpose of conducting elections. Some reviewing officials adjusted the boundaries of the voting districts (VTDs) they submitted to conform to census block boundaries for data presentation purposes, and therefore a VTD for which Census 2000 provides data might not exactly represent the legal entity; the Census Bureau refers to such VTDs as pseudo-voting districts (pseudo-VTDs). Such VTDs, as well as any others for which state officials did not specify a status, are identified by a “P ” in the VTD indicator field of the Public Law (PL) data file.

Statistical Entities

Statistical entities usually evolve from practice, custom, usage, or need, and generally the Census Bureau develops criteria and guidelines for their identification and delineation. They include:

Block Group (BG)

Census Block

Census County Divisions (CCD)

Census Designated Place (CDP)

Census Regions and Divisions

Census Tract

Metropolitan Area (MA)

Public Use Microdata Area (PUMA)

Rural

Urban

Urbanized Area (UA)

Urban Cluster (UC)

ZIP Code Tabulation Area (ZCTA)

Block Group (BG). A statistical subdivision of a census tract. A BG consists of all tabulation blocks whose numbers begin with the same digit in a census tract. BGs generally contain between 300 and 3,000 people, with an optimum size of 1,500 people. The BG is the lowest-level geographic entity for which the Census Bureau tabulates sample data from a decennial census.

Census Block. An area bounded on all sides by visible and/or nonvisible features shown on a map prepared by the Census Bureau. A block is the smallest geographic entity for which the Census Bureau tabulates decennial census data. The census blocks were completely renumbered for Census 2000 using 4-digit numbers.

Census County Divisions (CCD). A statistical subdivision of a county, established and delineated cooperatively by the Census Bureau and state,local, and tribal officials for data presentation purposes. CCDs have been established in 21 states.

Census Designated Place (CDP ). A geographic entity that serves as the statistical counterpart of an incorporated place for the purpose of presenting census data for an area with a concentration of population, housing, and commercial structures that is identifiable by name, but is not within an incorporated place. CDPs usually are defined cooperatively with state, local, and tribal officials based on Census Bureau guidelines. For Census 2000, for the first time, CDPs did not have to meet
minimum population threshold to qualify for the tabulation of census data. Note: A CDP in Puerto Rico is called a comunidad or zona urbana.

Census Regions and Divisions. The 50 states and the District of Columbia have been grouped into four regions, each containing two or three divisions.

Census Tract. A small, relatively permanent statistical subdivision of a county or statistically equivalent entity, delineated for data presentation purposes by a local group of census data users or the geographic staff of a regional census center in accordance with Census Bureau guidelines. Census tracts generally contain between 1,000 and 8,000 people. Census tract boundaries are delineated with the intention of being stable over many decades, so they generally follow relatively permanent visible features. However, they may follow governmental unit boundaries and other invisible features in some instances; the boundary of a state or county is always a census tract boundary. Block Numbering Areas (BNAs) are now called census tracts.

Metropolitan Area (MA). A large population nucleus, together with adjacent communities that have a high degree of economic and social integration with that nucleus. (Some MAs are defined around two or more nuclei.) MA is a collective term, established by the federal Office of Management and Budget in 1990, to refer to metropolitan statistical areas (MSAs), consolidated metropolitan statistical areas (CMSAs), and primary metropolitan statistical areas (PMSAs).

Metropolitan Statistical Area (MSA). An MSA is a metropolitan area (MA) that is not closely associated with another MA. An MSA consists of one or more counties, except in New England, where MSAs are defined in terms of county subdivisions (primarily cities and towns).

Primary Metropolitan Statistical Area (PMSA). If an area that qualifies as a metropolitan area (MA) has a population of 1,000,000 or more, two or more primary metropolitan statistical areas (PMSAs) may be defined within it if they meet official standards and local governments favor that designation. When PMSAs are established within an MA, that MA is designated a
consolidated metropolitan statistical area.

Consolidated Metropolitan Statistical Area (CMSA). An area becomes a CMSA if it qualifies as a metropolitan area, has a population of 1,000,000 or more, has component parts that qualify as primary metropolitan statistical areas (PMSAs) based on official standards, and local governments favor the designation. CMSAs consist of whole counties except in New England, where they consist of county subdivisions (primarily cities and towns).

Public Use Microdata Area (PUMA). A geographic entity for which the U.S. Census Bureau provides specially selected extracts of raw data from a small sample of long-form census records that are screened to protect confidentiality of census records. The extract files are referred to as public use microdata samples (PUMS). Public use microdata areas (PUMAs), which must have a minimum census population of 100,000 and cannot cross a state line, receive a 5-percent sample of the longform records; these records are presented in state files. These PUMAs are aggregated into super-PUMAs, which must have a minimum census population of 400,000 and receive a 1-percent sample in a national file. PUMAs and super-PUMAs are mutually exclusive, that is, they use different records to create each sample. Data users can use these files to create their own statistical tabulations and data summaries.

Rural. All territory, population, and housing units located outside of urbanized areas and urban clusters.

Urban. All territory, population, and housing units located within urbanized areas and urban clusters.

Urbanized Area (UA). Densely settled area that has a census population of at least 50,000. The geographic core of block groups or blocks must have a population density of at least 1,000 people per square mile, and adjacent block groups and blocks with at least 500 people per square mile.

Urban Cluster (UC). Consists of a geographic core of block groups or blocks must have a population density of at least 1,000 people per square mile, and adjacent block groups and blocks with at least 500 people per square mile that together encompass a population of at least 2,500 people, but fewer than 50,000 people.

ZIP Code Tabulation Area (ZCTA). A statistical entity developed by the Census Bureau to approximate the delivery area for a U.S. Postal Service five-digit or three-digit ZIP Code in the U.S. and Puerto Rico. A ZCTA is an aggregation of census blocks that have the same predominant ZIP Code associated with the mailing addresses in the Census Bureau ’s Master Address File. Thus, the Postal Service’s delivery areas have been adjusted to encompass whole census blocks so that the Census Bureau can tabulate census data for the ZCTAs. ZCTAs do not include all ZIP Codes used for mail delivery.

There are both legal and statistical American Indian, Alaska Native, and native Hawaiian entities for which the Census Bureau provides data for Census 2000. The legal entities consist of federally recognized American Indian reservations and off-reservation trust land areas, the tribal subdivisions that can divide these entities, state recognized American Indian reservations, Alaska Native Regional Corporations, and Hawaiian home lands. The statistical entities are Alaska Native village statistical areas, Oklahoma tribal statistical areas, tribal designated statistical areas, and state designated American Indian statistical areas. Tribal subdivisions can exist within the statistical Oklahoma tribal statistical areas.

TIGER

During the 1980 Census, the Census Bureau matched its population statistics to maps, which were drawn and produced by hand. These maps were difficult to maintain because they were often out of date and inaccurate. To solve this problem, the Census Bureau developed the TIGER Line files. TIGER (Topologically Integrated Geographic Encoding and Referencing) is the most comprehensive database of digital mapping information, including roads, highways and census boundaries for the entire United States. TIGER provides the capability of integrating census statistics with relevant geographic areas more efficiently and accurately.

Presently, PERCEPT is using an enhanced TIGER database produced by Geographic Data Technology, or GDT (acquired by Tele Atlas in 2004). The TIGER Files provide the geographical basis for all 1990 and 2000 Census data. Claritas has used GDT-enhanced versions of these files to geocode both addresses and intersections in metropolitan and rural areas.

Note: Information on the Census is derived from technical documentation from the Census Bureau, as well as a technical White Paper provided by Claritas to its information clients and adapted here with permission. See www.census.gov for more information about TIGER.