Redistricting Glossary
Advisory commission
A body charged with researching or advising on redistricting. In some states where the legislature has final authority over redistricting, advisory commissions have been created to recommend new maps. Advisory commissions have no authority to enact maps, and their recommendations may be adopted or rejected. Members may be legislators, non-legislators or both. Processes vary by state.
Alternative population base
A count other than total population from the federal decennial census that is used for redistricting.
Apportionment or Reapportionment
The process of assigning seats in a legislative body among preexisting political subdivisions such as states or counties. In the past, some states assigned districts on the basis of county boundaries and therefore continue to call their redistricting process "apportionment.”
At-large
A method of election in multimember districts. All candidates run against each other on one ballot, and they are elected by the whole population of the district.
Census
A complete count or enumeration of the population. The federal census is mandated by the U.S. Constitution in Article 1, section 2.
Census block
The smallest and lowest level of geography defined for decennial census tabulations. States may give input on block boundaries during the first phase of the Redistricting Data Program, called the Block Boundary Suggestion Project. The Census Bureau provides redistricting data down to the block level. Blocks can have any population, including zero people.
Census block group
Clusters of census blocks within the same census tract that have the same first digit of their four-digit census block number. Block groups generally contain between 600 and 3,000 people. Block groups often follow neighborhoods. They are used to present data and control block numbering. Localities can delineate block groups during the Census Bureau’s Participant Statistical Areas Program.
Census Bureau
The U.S. Bureau of the Census, part of the Department of Commerce, conducts the decennial Census of Population and Housing and numerous ongoing federal government projects. The bureau’s mission is to “Count Everyone Once, Only Once and in the Right Place” in the decennial census.
Census geography
The geographic units for which census information is tabulated and reported with several hierarchies. The most basic unit is the census block. Other units include census block group, census tract, county and state.
Census tract
Census tracts are small, relatively permanent geographic entities within counties (or the statistical equivalents of counties) delineated by a committee of local data users. Generally, census tracts have between 2,500 and 8,000 residents and boundaries that follow visible features. Census tracts were originally intended to be as homogeneous as possible with respect to population characteristics, economic status, and living conditions. Tracts were first defined in 1970 and the Census Bureau maintains them as consistently as possible across the decades.
Coalition district
Electoral districts with multiple minority groups that, individually, do not meet the requirements for a majority-minority district under Section 2 of the Voting Rights Act, but do when combined as a coalition.
Commission
A statutory or constitutional body charged with researching, advising or enacting new redistricting maps. Redistricting commissions have been used to draw districts for legislatures and Congress. Members may be legislators, non-legislators or both. Commissioner selection policies vary by state. Commissions may be part of the legislature or a separate entity.
Communities of interest
Geographical areas, such as neighborhoods of a city or regions of a state, where the residents have common demographic and/or political interests that may not coincide with other political subdivision boundaries such as city or county lines.
Compactness
Having the minimum distance between all the parts of a constituency (a circle, square or a hexagon are examples of a very compact district). Various methods have been developed to measure compactness.
Contiguity
All parts of a district being connected geographically at some point with the rest of the district. Limits on contiguity by point or by water vary by state.
Citizen population
The total number of US citizens counted in a census block or other geographic area.
Citizen voting age population
Includes all individuals over the age of 18 who are citizens.
Cracking
A term used when a redistricting plan divides a particular group in a way that lessens its political influence.
Deviation
The measure of how much a district or plan varies from the ideal population, however defined, per district. Deviation can be expressed as an absolute number or as a percentage.
District
The boundaries that define the constituency from which a public official is elected.
Gerrymander
A term of art used to describe a plan or a district intentionally drawn to advantage one group or party over another, sometimes identified by bizarre shapes.
GIS
Geographic Information System. Computer software used for creating or revising plans and analyzing geographically oriented data.
Ideal population
The total population or alternative for the state or top-level jurisdiction divided by the number of seats in a legislative body.
Influence district
Term used to describe a district where a racial minority does not constitute a majority but is populous enough to influence electoral outcomes.
Majority-minority districts
Term used by courts for districts where a group or a single racial or language minority constitutes a majority of the population.
Metes and bounds
A highly detailed description of district boundaries using specific geographic features and street directions. Similar to how real property is described for legal purposes. Metes and bounds are rarely used today. Most enabling legislation points to maps to describe districts.
Minority opportunity district
A district that allows minority voters to elect its preferred candidate of choice in which the minority population does not make up 50% or more of the district.
Multimember district
A single district that elects two or more members to a legislative body, as opposed to a single-member district.
Natural boundaries
District boundaries that follow natural geographic features such as bodies of water or mountains.
Nested
When multiple districts of a legislature’s lower chamber are wholly contained within the geographic boundaries of one of the upper chamber's districts.
One person, one vote
A constitutional standard established by the U.S. Supreme Court that means all districts for representational bodies should be approximately equal in population. The degree of equality may vary in congressional plans and legislative or local plans.
Overall range
The difference in population between the largest and smallest districts in a districting plan in either absolute (persons) or relative (percentage) terms.
Packing
A term used when a redistricting plan consolidates a particular group in a small number of districts, causing the group to constitute a supermajority in those districts and lessening its political influence in nearby districts.
Plan
A set of boundaries for all districts of a representational body. Often referred to as a map.
PL 94-171
Federal law enacted in 1975 requiring the U. S. Bureau of the Census to provide the states with data for use in redistricting as well as mandating the program where the states define the geography for collecting data.
Racially Polarized Voting (RPV)
Racially polarized voting occurs when voters from different racial or ethnic groups show significantly different preferences for candidates in an election. Statistical analysis is used to identify the presence of racially polarized voting in a jurisdiction.
Redistricting
The redrawing or revision of boundaries for representational districts.
Section 2 of the Voting Rights Act
Federal law that protects racial and language minorities from discrimination at the hands of the state, or another political subdivision, in voting practices.
Section 5 of the Voting Rights Act
Federal law that requires certain states and localities to preclear all election law changes with the U.S. Department of Justice or the federal district court for the District of Columbia before those laws take effect. Section 5 is limited in scope since the 2013 Shelby County v. Holder decision, in which the U.S. Supreme Court invalidated Section 4(b) of the VRA. Section 4(b) determined which jurisdictions were subject to preclearance. This decision effectively suspended Section 5 of the VRA.
Single-member district
District electing only one representative, as opposed to a multimember district.
Single-member election
Election in which only one candidate is elected. While all single-member district elections are single-member elections, single-member elections can occur in multimember districts if seats within the district are not all elected at the same time.
Tabulation
The totaling and reporting of the census data from individual responses for all levels of census geography.
Voting Age Population (VAP)
The number of persons 18 years of age and over. BVAP indicates Black Voting Age Population, HVAP indicates Hispanic Voting Age Population, and so on.
Voting district
A census term for a geographic area, such as an election precinct, where election information and data are collected. States provide voting district boundaries to the Census Bureau. Boundaries must coincide with census blocks and therefore may differ from election precinct boundaries. Voting districts may include all or part of multiple precincts.