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Apportionment: The process of allocating a fixed number of seats in a governmental body among established political units. Following each decennial census, the seats in the U.S. House of Representatives are reapportioned among the states. The result is that each state is assigned its number of congressional seats for the next decade. Reapportionment does not result in the establishment of new district boundaries. The term is sometimes used imprecisely to mean redistricting.
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Census Block: The smallest unit of census geography for which population data are reported. Census blocks are designated by the Census Bureau and are generally bounded by visible physical features such as roads, creeks, or railroads, though in some cases they may be bounded by non-visible features such as city limits.
Census Block Group: A cluster of census blocks within a census tract designated by the Census Bureau as a subdivision of that census tract.
Census Data: Information and statistics on the population of the United States gathered by the Census Bureau and released to the states.
Census Tract: A unit of census geography defined by the Census Bureau for the purpose of presenting decennial census data. Census tracts are made up of block groups. Their boundaries generally follow visible features, though in some circumstances their boundaries may follow governmental unit boundaries or other non-visible features. In general, census tracts must contain between 1,500 and 8,000 inhabitants.
Community of interest: A grouping of people concentrated in a geographic area, such as in a city or a neighborhood that share similar political, social, or economic interests.
Compactness: A term used to describe a district’s geographic shape. Compactness in redistricting cases often focuses on the regularity or jaggedness of a district boundary and on the extent to which the district’s geographic territory is dispersed from its center.
Contiguity: Adjacency. For redistricting purposes, a district is considered to be contiguous if all parts of the district are connected to each other, so that the entire district is within a continuous boundary. Legal standards governing redistricting for various governmental bodies often require all of the territory in each district to be contiguous.
County Election Precincts: Geographic units established for the purpose of election administration. The voters in an election precinct usually vote at a single polling place, so the votes cast in the precinct may be counted separately from other precincts.
Cracking or Fracturing: A form of dilution occurring when districts are drawn so as to divide a geographically compact group of people with the same characteristics, for example, a minority community into two or more districts. If the minority community is politically cohesive and could elect a preferred candidate if placed in one district, but, due to cracking, the minority population is divided into two or more districts where it no longer has any electoral control or influence, the voting strength of the minority population is diluted.
Crossover District: One in which minorities do not form a majority, but still reliably control the outcome of the election with some non-minority voters crossing over to vote with the minority group.
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Deviation: The amount by which a district’s population differs from the ideal population. The deviation is the amount of population that is less than or greater than the ideal population of a district. In redistricting, a slight deviation may be permissible if based on rational state policies.
Differential undercount: The extent to which one group of persons is more likely to be undercounted in the decennial census than other groups. For example, in the 1990 census, though almost 100 percent of white persons were counted, approximately 5 percent of black and Hispanic persons were not counted. See “Undercount.”
Dilution or Vote Dilution: Occurs when the voting strength of a politically cohesive minority group is weakened or watered down by an election system, redistricting plan, other electoral process or procedure. For example, the creation of districts that either (1) divide cohesive members of a racial or ethnic minority group among several districts, artificially reducing the group’s opportunity to influence elections or (2) place extraordinarily high percentages of members of a racial or ethnic minority group in one or more districts, so that minority voting strength is artificially limited to those districts and is minimized in neighboring districts.
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Equal Protection Clause: See “Fourteenth Amendment to the U.S. Constitution.”
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Fourteenth Amendment to the U.S. Constitution: The U.S. Constitution provision that includes the Equal Protection Clause, which prohibits the state from denying persons equal protection of the law. The Equal Protection Clause is the primary basis of the one-person, one-vote principle.
Fifteenth Amendment to the U.S. Constitution: The U.S. Constitution provision indicating that the right to vote may not be denied or abridged on account of race.
Fragmentation: The division of a geographically concentrated cohesive group, such as a racial or political group, among different districts for the purpose of minimizing the group’s voting strength.
Fracturing: See definition of “Cracking.”
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Geographic Information System (GIS): A graphics-based computer system that relates geographic features (such as census tracts, roads, or counties) to data about those features (such as population, race, or income).
Gerrymander: A district or set of districts typically characterized by unusual boundaries, which is drawn to favor one or more individual interest groups over others or to increase the likelihood of a particular political result.
Gingles Factors: The three preconditions set forth by the U.S. Supreme Court in Thornburg v. Gingles, 478 U.S. 30 (1986), that a minority group must prove to establish a violation of Section 2 of the Voting Rights Act. The preconditions are: 1) a minority group must be sufficiently large and geographically compact to comprise a majority of the district; 2) the minority group must be politically cohesive (it must demonstrate a pattern of voting for the same candidates); and 3) White voters vote sufficiently as a bloc usually to defeat the minority group’s preferred candidate.
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Homogenous Precinct/Homogenous District: A precinct or district that is nearly all of one race, usually more than 80 percent of one racial group.
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Ideal Population: The number of persons to be placed in each district to obtain equal population. The ideal population for each district is obtained by taking the total population of the state or jurisdiction and dividing it by the number of districts to be redistricted in the state or jurisdiction.
Influence District: Where a minority group constitutes a less than controlling voting group in a district but nevertheless constitutes such a sizeable minority in the district so that they can influence the outcome of an election.
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Majority – Minority District: A district where a minority group usually constitutes the majority of voters and can control the outcome of elections.
Method of Equal Proportions: The mathematical formula used, as provided by federal statute, to reapportion congressional seats among the states after each decennial census.
Minority-coalition district: One in which two or more minority groups combine to form a majority in a district.
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One Person, One Vote: The principle that each person’s vote should count equally with every other person’s vote, which is effected by the allocation of the same or substantially the same population to each district of a particular type, such as a congressional district. The courts derive the one-person, one-vote standard primarily from the Equal Protection Clause of the Fourteenth Amendment to the U.S. Constitution. This also includes the concept that each person in a district (including those not eligible to vote) is entitled to representational equality, that is to have the same access to the elected representative as each person in every other district.
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Packing: Drawing districts in a way that puts as many people with the same characteristics into as few districts as possible. Creating a district with a very high concentration of a particular group of voters, such as a racial or political group, tending to result in the election of the group’s candidate of choice in any election in that district and the dilution of the group’s voting strength in neighboring districts.
P.L. (Public Law) 94-171: The federal statute that requires the Census Bureau to provide, by April 1 of each year following a decennial census, the population and race data necessary for redistricting.
Political Subdivision: A division of a state; in California, counties.
Population Estimates: An approximation of the population of a geographic unit at a point in the past or present for which an actual population count is not available.
Population Projections: An approximation of the population of a geographic unit at a point in the future based on specific assumptions regarding future demographic trends in the geographic unit.
Precinct: An area created by election officials to group voters in a designated polling place so that an election can be conducted.
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Racially-Polarized Voting: The term used to describe circumstances in which the voting preferences of a racial or ethnic group consistently vary from those of other racial or ethnic groups, particularly when the different voting preferences are based on the race of the candidate; also referred to as “racial bloc voting.”
Redistricting: The process utilizing the 2010 population statistics from the Census Bureau to redraw the boundaries of electoral districts to ensure the districts are equal in population as can be. The process impacts all levels of government.
Redistricting Data Unit or Redistricting Unit (RDU): These are primarily census tracts within the County of Los Angeles from which data have been compiled for use in the redistricting software.
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Statistical Sampling: The statistical method by which characteristics of a small group are measured and applied to the population as-a-whole.
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Topologically Integrated Geographic Encoding and Referencing System (TIGER): The cartographic map database, prepared by the Census Bureau, which contains the geographic base units (census tracts) that will be used for redistricting.
Total Range of Deviation: The range over which the populations of all districts in a redistricting plan deviate from the ideal, target or average district population.
Traditional Districting Principles: Factors traditionally used by a state or local jurisdiction to perform redistricting. Examples of traditional redistricting principles may include: compactness, contiguity, respect for political subdivisions, respect for communities of interest, and protection of incumbents.
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Undercount: The error in census data that results from the failure to count some persons or housing units in the decennial census. Historically, certain groups, such as members of racial or ethnic minorities, have been disproportionately undercounted by the federal census.
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Voting Age Population: This is the number of persons in a geographic unit who are at least 18 years of age. Because some population groups, such as racial or ethnic minorities, tend to be younger on average than the population as a whole, the voting age populations are frequently compared in evaluating the potential voting strength of those groups.
Voting Age Citizen Population: The number of persons in a geographic unit who are age 18 plus and who, as citizens, are eligible to vote.
Voting Rights Act: The Federal statute prohibiting discrimination in voting practices on the basis of race or language group, codified as 42 U.S.C. Section 1973 et seq. The official title of the Act is the Voting Rights Act of 1965. The Act was amended in 1982. Sections 2 and 5 of the Act are important for redistricting.