Bay Area Census -- Glossary

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

A full census glossary is available from the U.S. Census Bureau here.

Block group
A subdivision of a census tract (or, prior to 2000, a block numbering area), a block group is the smallest geographic unit for which the Census Bureau tabulates sample data. A block group consists of all the blocks within a census tract with the same beginning number.

Example: block group 3 consists of all blocks within a 2000 census tract numbering from 3000 to 3999. In 1990, block group 3 consisted of all blocks numbered from 301 to 399Z.

Census block
A subdivision of a census tract (or, prior to 2000, a block numbering area), a block is the smallest geographic unit for which the Census Bureau tabulates 100-percent data. Many blocks correspond to individual city blocks bounded by streets, but blocks – especially in rural areas – may include many square miles and may have some boundaries that are not streets. The Census Bureau established blocks covering the entire nation for the first time in 1990. Previous censuses back to 1940 had blocks established only for part of the nation. Over 8 million blocks are identified for Census 2000.

Census designated place (CDP)
A statistical entity, defined for each decennial census according to Census Bureau guidelines, comprising a densely settled concentration of population that is not within an incorporated place, but is locally identified by a name. CDPs are delineated cooperatively by state and local officials and the Census Bureau, following Census Bureau guidelines. Beginning with Census 2000 there are no size limits.

Census tract
A small, relatively permanent statistical subdivision of a county delineated by a local committee of census data users for the purpose of presenting data. Census tract boundaries normally follow visible features, but may follow governmental unit boundaries and other non-visible features in some instances; they always nest within counties. Designed to be relatively homogeneous units with respect to population characteristics, economic status, and living conditions at the time of establishment, census tracts average about 4,000 inhabitants. They may be split by any sub-county geographic entity.

Census tract/block outline maps*
A map showing the census tract and block borders in a county; may be used to assist in determining the correct identifying number for the desired area.

Diversity Index Calculation
In terms of calculation, the proportion of population in a group is multiplied by the natural log of that proportion, e.g., 50 percent white is calculated as: 0.50 * log(0.50) = -0.3466. In the special case of a 0.00 proportion, the product of this calculation is defined as 0.00. These five numbers are then summed and divided by -1.609. The following example is for the City of Oakland:

Geographic Information Systems (GIS)*
A computer system used for storing, integrating, manipulating, analysing and displaying data related to geographic position. Typically, a GIS map has several different layers, with each layer holding data about a particular kind of feature (e.g. roads). Each feature is linked to a position on the graphical image of a map.

Public Use Microdata Area (PUMA)
An area that defines the extent of territory for which the Census Bureau tabulates public use microdata sample (PUMS) data.

Public Use Microdata Sample (PUMS) files
Computerized files containing a small sample of individual records, with identifying information removed, from the census long form and from the American Community Survey showing the population and housing characteristics of the people included on those forms. Provides more detailed data than other census files, but only for a small sample of the population.

TIGER database
TIGER ® is an acronym for the Topologically Integrated Geographic Encoding and Referencing (System or database). It is a digital (computer-readable) geographic database that automates the mapping and related geographic activities required to support the U.S. Census Bureau’s census and survey programs. The U.S. Census Bureau developed the TIGER System to automate the geographic support processes needed to meet the major geographic needs of the 1990 census: producing the cartographic products to support data collection and map presentations, providing the geographic structure for tabulation and dissemination of the collected statistical data, assigning residential and employer addresses to the correct geographic location and relating those locations to the geographic entities used for data tabulation, and so forth. The content of the TIGER database is undergoing continuous updates and is made available to the public through a variety of TIGER/Line ® files that may be obtained free of charge from the Internet or packaged on CD-ROM or DVD from Customer Services, U.S. Census Bureau, Washington, DC 20233-1900.