Redistricting is the process of redrawing election boundaries to equalize population, but you might ask; what population? and whether states and local jurisdictions have a choice in the matter. The short answer is that up to this point the overwhelming majority of jurisdictions use “total population” to measure equality among districts. The Supreme Court has acknowledged that states can use various population bases (provided they do not discriminate), but it has so far refused to mandate any specific method in particular. Here are the various potential measures of equal population:
Total Population: This is the standard method because it is easily accessible from decennial census data. This dataset includes citizens and non-citizens voting age and under, and is the most detailed dataset because the Census Bureau reports it down to the smallest geographic reporting level – which is in many cases, as small as a city street block.
Citizen Voting Age Population (CVAP): This measure of all adult, voting-age individuals who are citizens, is only available in estimate form since the decennial census does not have a citizenship question. However, the annual American Community Survey (ACS) conducted by the U.S. Census Bureau does ask about citizenship and provides estimates for large cities and other municipalities. The data differs from the decennial census in that it is not a complete count of citizens and is based on a survey. This dataset is used in redistricting, however, but mostly when drawing specific districts that are required under the Voting Rights Act (VRA). For instance, if a court finds that two congressional districts in a state are protected under Sec. 2 of the VRA, it may redraw those districts using CVAP data to ensure that the protected minority will actually be able to elect a candidate of their choice.
During the Trump administration, the U.S. Census was directed to create a special tabulation of CVAP that would be as detailed as the decennial census data, thus citizen voting-age population could be used more readily as a population base for redistricting. The Bureau was tasked with finding an alternate source for this citizenship information after a proposed citizenship question for the census was rejected by courts. The Bureau abandoned work on this special tabulation in February of 2021.
Total Voter Registration: This measure is not currently used for any state congressional or legislative maps, however, a 2015 Texas lawsuit did ask courts to require that districts be redrawn to equalize total registered voters (or at least the citizen voting-age population). The idea behind the suit was that the one-man-one-vote principle that requires equally populated districts was adopted precisely to ensure that “voters” votes would be equally weighted. When voters are put into districts with nonvoters or non-citizens, their voting power can be easily diluted across districts. In the end, the Supreme Court declined to make total voter registered voters the required metric for redistricting, nor did it advocate its use. Read a discussion of the opinion on SCOTUSblog.
State Citizenship: Hawaii’s 1950 constitution recognized state citizenship as an appropriate population measure for redistricting and the U.S. Supreme Court in 1966 recognized the measure as an appropriate one because of the large number of military stationed in the state. This measure is not widely used but at least one other state (Kansas) has adjusted population data in the past to exclude students and members of the military. It recently ended the practice.
Prisoners: The prison population has also come up as an equal population issue in the last decade, not because there is serious debate about whether to count prisoners or not, but the question has become “where” to count them. The decision on whether to count prisoners at home or at the institution they are being held has equal population implications since large concentrations of prisoners could artificially inflate the population of a district much like the plaintiffs in the Texas suit argued that large concentrations of noncitizens or nonvoters would dilute the voting power of registered or eligible voters. The Supreme Court has upheld the practice of counting prisoners at their previous home address (prisoner reallocation), provided it is done carefully. This Law Forum article on that case provides a look at how courts will approach prisoner reallocation processes in the future. Ten states currently reallocate prisoners for redistricting.
