What is redistricting data

Redistricting data is the collection of geographic, demographic, and electoral datasets used to draw and evaluate legislative district boundaries. Understanding what these datasets contain—and where they come from—is a prerequisite for any redistricting analysis.

Census blocks

The census block is the smallest geographic unit used by the U.S. Census Bureau. It is the atomic building block of all redistricting work. A census block is defined by visible features (roads, waterways, railroad tracks) and administrative boundaries. Georgia contains approximately 291,000 census blocks.

For redistricting, the most important product is the PL 94-171 redistricting data file, delivered to each state following the decennial Census. It provides total population, voting-age population (VAP), and race/ethnicity breakdowns at the block level. The 2020 PL file was delivered to states in August 2021.

District boundaries

District boundaries are stored as shapefiles—geospatial vector files that encode polygons representing each district. Shapefiles can be joined to census block data to calculate the population composition of any proposed or enacted district. The Redistricting Data Hub is a key source for Georgia district shapefiles, including historical boundaries from past cycles.

Population counts

The core requirement of redistricting is "one person, one vote" (population equality). Districts within a legislature must have roughly equal total populations. For congressional districts, courts require near-perfect equality. For state legislative districts, a deviation of up to ±5% from the ideal population (total population ÷ number of districts) is generally acceptable.

CVAP — Citizen Voting Age Population

CVAP is total population minus: non-citizens, people under 18, and (in states that disenfranchise them) people with felony convictions. CVAP comes from the American Community Survey (ACS), specifically the Census Bureau's annual CVAP Special Tabulation. It is not a decennial Census product—it is a five-year ACS estimate and carries a margin of error.

CVAP matters for redistricting because Section 2 of the Voting Rights Act focuses on the ability of minority voters (citizens who are eligible to vote) to elect candidates of their choice—not on total population or VAP alone. When courts evaluate whether a proposed map dilutes minority voting power, they typically look at CVAP for the affected group, not raw population.