Glossary of Terms

  • American Community Survey (ACS): A survey that provides data in four categories every year. The categories are: social, demographic, economic and housing. The ACS replaced the “long form” of the census that was collected once every 10 years. The ACS does not report full counts of the population, but rather estimates. ACS data is sometimes used to determine legality of certain districts under the VRA.
  • Attribute data: Data object closely associated with or belonging to a geographic entity.
  • Census Block (Block): The smallest level of geography designated by Census Bureau. Blocks are bounded on all sides by visible features such as streets, roads, streams, and railroad tracks, and occasionally by invisible boundaries such as city limits or property lines. In rural settings, census blocks may cover large geographical areas, while in urban settings they often cover one city block. A block is usually the smallest geographic unit for which decennial census data are tabulated. Redistricting is based on census block-level data. Approximately 10 million blocks are identified in Census 2000.
  • Block Group (BG): Block Groups are a group of census blocks (see census block above) within a census tract, sharing the same first digit of their four-digit identifying numbers.
  • Census County Division (CCD, Unincorporated Place): A statistical area, defined for a decennial census, comprising a densely settled concentration of population that is not incorporated, but resembles an incorporated place in that it can be identified with a name by local people. The boundaries, which are usually marked by visible features or the boundary of a nearby census place, have no legal status, nor are there any officials elected to serve traditional municipal functions. These areas were called "unincorporated places" prior to the 1980 census.
  • Census Place (Place, Incorporated Place, CDP): Census Places are population concentrations, such as cities, that have legally prescribed boundaries, powers, and functions. Other population centers without legally defined corporate limits are defined by the Census Bureau, in cooperation with state officials and local data user,s as Census-Designated Places and can be identified in Data tables by the acronym CDP following the place name.
  • Census Tract: A small, relatively permanent statistical subdivision of a metropolitanarea or non-metropolitan county, identified for the purpose of presenting decennial census data. When census tracts are established, their boundaries are designed to have relatively homogeneous demographic characteristics and to contain between 2,500 and 8,000 inhabitants.
  • City: A type of incorporated place with legally established boundaries and powers. In California, there are two kinds of cities: charter cities and general law cities. Unlike cities in many other states, both kinds of California cities have broad powers and enjoy considerable freedom in the form of government that may be established and the types of activities in which they may engage.
    • Charter City: The authority provided in the state constitution to organize as a charter city is extended only to an existing city. Although general law cities now have nearly equal powers, charters are adopted by cities where special conditions create needs that cannot be adequately met by the state's general laws. A charter city can adopt a charter and custom-tailor its organization and elective offices to provide for unique local conditions and needs. A charter can only be adopted or changed by a majority vote of city residents--not by a vote of the city council. Citizens can establish the terms and number of council members and impose other limitations upon their city council through a charter provision.
    • General Law City: A general law city operates within the parameters and guidelines of California municipal law. The advantage of a general law city is that general state laws have been subjected to judicial scrutiny and tested over time, so there is relatively little confusion about their application. City charters, by contrast, can be much more complicated and can raise many more questions about what can and cannot be done under state law.
  • County: The primary subdivision of a State (except Alaska and Louisiana). A county usually is a governmental unit with powers defined by State Law.
  • Codebook: Defines the variables and codes that make up the data.
  • Datapoint: a single fact or piece of information; a datum.
  • Decennial Census (Census): Count of the U.S. population conducted every ten years by the Census Bureau.
  • Demographics: statistical characteristics of populations such as age, race, sex or income level.
  • District: A political area used primarily for voting purposes (election or voting district).
    • District Deviation: The difference, measured in people, of the current district population from the ideal district population for a district. The ideal district population is based on the total population of the state as recorded by the last Decennial Census released prior to redistricting.
    • Ideal District Population: The total population for the jurisdiction as reported by the Census P.L 94-171 dataset divided by the number of districts. The ideal population is the number of people that each district should contain when the redistricting process is complete.
  • Equivalency File: A GIS file that shows the relationship between two geographic units. In redistricting, this file usually lists each census block in the dataset and indicates which district each block belongs to. The collection of block assignments is read by GIS software and displayed as district lines.
  • Federal Information Processing Standards Code (FIPS code): Numeric codes assigned to uniquely identify U.S. counties and county equivalents (Alaska and Louisiana). In census files, the county FIPS codes are five-digits with the last three digits indicating the county and the first two digits designating the state FIPS code (which for California is 06). Please see our FAQ page for a list of FIPS codes for all California counties.
    • Geocoding: Placing a datapoint into a geographical location.
    • Geographical hierarchy: A system of relationships among geographical units wherein those geographical units are subdivided into lower-order units that in turn may be further subdivided. For example, States are subdivided into counties, which are further subdivided into minor civil division or census county divisions. Some census reports and summary tape files present data in the following"hierarchical sequence":
      • United States
      • Region
      • Division
      • State
      • County
      • Minor civil division (MCD)/census county division (CCD)
      • Place* or remainder of MCD/CCD
      • Census tract/block number area (BNA)*
      • Block group*/ enumeration district
      • Block
        • * The asterisks denote geographic entities that may cross the boundaries of higher-level units; that is, a place that exists partly in one MCD and partly in another. In a hierarchical presentation, the lower-level units must fit into the specified framework; that is, a place crossing the boundary between two MCD's would be shown as two place parts sequenced separately following the appropriate MCD records.
  • Geographic Information System (GIS): Software designed to "map" political and demographic data to geographic entities. Examples of commonly used GIS software include Google Earth, ArcGIS, QGIS, Maptitude, and MapInfo.
  • Metropolitan Area (MA): An area defined by the Office of Management and Budget as a Federal statistical standard. An MA consists of a population nucleus with at least 50,000 people, together with adjacent communities that have a high degree of social and economic integration with that core. Metropolitan areas comprise at least one county, except in New England, where cities and towns are the basic geographic units.
  • Minor Civil Division (MCD)/ Census County Division (CCD): MCDs are legally defined county subdivisions such as towns and townships. In 21 states where MCDs do not exist or are not adequate for reporting sub county statistics, the Census Bureau, in cooperation with state officials and local data users, delineates county subdivisions known as Census County Divisions.
  • Precinct: A political boundary periodically redrawn by the county registrar of voters. Multiple precincts may change in every election. Registration precincts differ from voting precincts. A precinct polygon refers to the shape of a precinct.
  • Racially Polarized Voting (RPV): Racially polarized voting occurs when voters of different races tend to vote for different candidates. For example, in an area where White voters tend to vote against the candidates for which Asian American voters cast their ballots, racially polarized voting is present.
  • Reapportionment: A constitutionally mandated re-allocation of Congressional seats amongst the states. Allocation is based on population.
  • Registration Statistics: Statistics related to registered voters.
    • REG - Statement of Registration data compiled for all registered voters.
    • ABS - Statement of Registration data for registered voters that voted by absentee ballot. Please note that these data are not available for all counties. Some county election offices do not differentiate between poll voters and absentee voters.
    • POLL_VOTE - Statement of Registration data for registered voters who actually voted at their precinct polling station. Please note that these data are not available for all counties. Some county election offices do not differentiate between poll voters and absentee voters and/or some counties do not have polling places.
    • VOTE - Statement of Registration data for those registered voters that actually voted.
  • Redistricting: A constitutionally mandated redrawing of local, state, and federal political boundaries every ten years following the Decennial Census. The lines of Assembly, Senate, and Congressional Districts are redrawn to reflect changing demographics and population shifts. Local political boundaries, such as city council district boundaries, are redistricted as well.
  • Redistricting (Public Law 94-171) Summary File: The first Census released, the PL 94 is the information required for local and statewide redistricting. The data will include tabulations by 63 race categories, cross-tabulated by "not Hispanic or Latino" for the total population and the population 18 years and over. Detailed tabulations will present data down to the block level, and will be available through two CD-ROM series (state and national files). One Quick Table and Geographic Comparison Table will be based on this redistricting file.
    • NOTE: The Public Law 94-171 numbers are expected to reflect corrections for possible overcounts and undercounts using measurements from the Accuracy and Coverage Evaluation survey. To fulfill the requirements of Public Law 105- 119 (enacted in 1997), the Census Bureau also must make publicly available a second version of these data that does not include the statistical corrections for overcounts and undercounts measurements in the Accuracy and Coverage Evaluation.
    • Summary File 1 (SF 1)- Presents counts and basic cross-tabulations on information collected from all people and housing units. This information includes age, sex, race, Hispanic or Latino origin, household relationship, and whether the residence is owned or rented. Data will be available down to the block level for many tabulations, but only to the census-tract level for others. Summaries will also be included for other geographic areas such as ZIP Code Tabulation Areas and Congressional Districts.
    • Related products include Demographic Profiles that will give a snapshot of the geographic area, Quick Tables, Geographic Comparison Tables, and the first of the printed report series (See below). Summary File 2 (SF 2)- Will contain 100-percent population and housing characteristics, but the tables in this file will be iterated for a selected list of detailed race and Hispanic- or Latino-origin groups, as well as American Indian and Alaska Native tribes. For this file, the lowest level of geography will be the census tract, and there will be a population-size threshold before information is shown for a particular group. Various Quick Tables and Geographic Comparison Tables will be derived from Summary File 2. Summary File 3 (SF 3)- Will be the first release of the information collected on a sample basis. Data will be provided down to the block group for many tabulations but only down to the census tract for others. SF 3 will also include data by ZIP Code Tabulation Area and Congressional District. Related products include three-page profile report, various Quick Tables, and Geographic Comparison Tables, and a printed report series, developed from the sample data.
    • Summary File 4 (SF 4)- Will include tabulations of the population and housing data collected from a sample of the population. Just as in Summary File 2, the tables on SF 4 will be iterated for a selected list of race and Hispanic- or Latino-origin groups, for American Indian and Alaska Native tribes, as well as for ancestry groups. Various Quick Tables and Geographic Comparison Tables will be derived from Summary File 4.
    • Registrar of Voters: A county-level government agency that maintains voting registration information and releases voting results by precinct.
    • Shapefile: A geographic data format created by ESRI, which consists of three different files: SHP, SHX, DBF. We distribute geographical information via shapefiles.
    • Summary File: (see Redistricting Summary File).
  • Standard Tape File 3 (STF 3): Data released at block group level by the Census Bureau. Contains detailed information on the demographics, income, employment, and family life of the residents of a given block group.
  • Statement of Vote (SOV): Election data collected by the Registrars of Voters in the individual counties. The SOV is reported on the Election Precinct level.
  • Statement of Registration (SOR): Registration data compiled by the Registrars of Voters. The SOR includes party identification among other variables.
  • Topographically Integrated Geographically Encrypted Reference (TIGER): The census geography used in the Statewide Database for geocoding is based on the TIGER file.
  • Variable: an alphanumeric code that describes a piece of data defined in the codebook.
  • Voting Districts: Voting districts represent areas created for the purpose of conducting elections. They include election districts, precincts, wards, polling areas, and other types of electoral units submitted to the Census Bureau by states participating in the Redistricting Data Program.
  • Voting Rights Act (VRA): The Voting Rights Act was originally passed in 1965 to prohibit discrimination on the basis of race or ethnicity. It has been amended several times, and now also prohibits discrimination based on membership of certain language minority groups.
    • California Voting Rights Act (CVRA): Passed in 2001, the CVRA expands on the federal Voting Rights Act, making it easier for minority groups in California to prove that their votes are being diluted in "at-large" elections. Certain cities that have never had minority representation or have a history of minority candidate suppression can be liable for damages and forced to change to district elections.

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