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Voter File Data

This article explains what voter file data are, how they are collected and processed, and where they can be accessed on the Redistricting Data Hub website.

Overview

Voter file records contain the information from the voter registration form and whether someone voted in a given election. They do not indicate for whom an individual voted because the US uses a secret ballot system, meaning that ballots do not contain information about the voter or their demographics. Voter file data is collected and maintained by individual counties. Since the Help America Vote Act of 2002, all states are required to maintain a computerized statewide voter file. However, states have different rules regarding who can access these files and for what purposes they can be used. In some states, raw voter file data are collected and maintained by individual counties. Commercial vendors purchase, merge, and clean these data, then append numerous other variables gleaned from public and commercial sources. The RDH obtained voter files from the L2 database.

How are voter file data used in redistricting?

Voter file data are useful for understanding the population of eligible voters and may be used for racially polarized voting (RPV) analyses. It may also be used in analyses of partisan gerrymandering.

Who is included in the data?

Raw voter files contain anyone in the Citizen Voting Age Population (CVAP) who has registered to vote. They are updated after each election to reflect whether an individual voted and (sometimes) the method by which they cast their vote. Commercial vendors also continuously update their files.

If you are downloading data for North Dakota, be aware that voter file data are modeled due to the fact that there is no voter registration requirement. The modeling is based on public and private data sources, such as exit polling from presidential elections, commercial lifestyle indicators, census data, and self-reported party preferences from private polling. Combining all of these data sets through Bayesian analysis and other statistical techniques has resulted in the likely party affiliations the RDH has applied to the voter files in North Dakota. For more detail, see the metadata for the voter file dataset you are downloading from North Dakota.

In addition, most states have some restrictions against felons voting. The Sentencing Project has more information on state felony disenfranchisement restrictions in 2020.

How are the data collected and processed?

The information collected varies by state. Typically, a voter file will contain a voter’s name, address, and voting history, but it may also contain other information, including but not limited to emails, phone numbers, racial identification, and partisan identification. The National Conference of State Legislatures (NCSL) breaks this down state by state. L2 uses modeling techniques for some fields such as ethnicity and party affiliation. Commercial voter files include all the previous information, plus up to hundreds more fields with known and predicted attitudes and behaviors. Commercial vendors purchase the data, standardize the field names, and merge the data with other information from public records and other outside sources, such as credit bureaus and consumer data. As a result, commercial voter file data may also include non-registered voters. These files often contain predictions about the attitudes and behaviors of the individual, based on proprietary models. Commercial voter files are regularly used by candidates, parties, interest groups, and other organizations for campaigning and outreach.

In addition, states may clean, or “purge” voter rolls by dropping voters who fail to meet certain requirements (e.g., by not responding to notices, or not voting in the last few elections). They also use the Postal Service change of address service and audit death records, among other data sources, to maintain accuracy.

The RDH obtained voter files from the L2 database. L2 assigned each voter to a 2010 Census Block on their Voter File. They also provided the RDH with a file that has each individual and their corresponding 2020 Census Block. The RDH joined the L2 Voter File to this 2020 Census Block assignment file and then aggregated the individual level Voter File to the Census Block level.

The RDH hosts 2021 voter file data aggregated to both 2010 and 2020 census geographies. The 2021 voter file contains voting history with counts of voters registered in 2021 who voted in previous elections. However, voter files change over time as voters get added or dropped, meaning that counts of voters in more recent elections will be more reliable in terms of representing the electorate. In addition to the Census Block level, the RDH also hosts voter file data aggregated to the Census VTD level. For more information about the methodologies specific to each file, view the metadata for the file you would like to download.

Where can the data be found on the Redistricting Data Hub website?

Voter files can be found in each state’s download page by selecting “Voter Files” in the “Filter by Type of Data” dropdown menu, or by selecting “L2” in the “Filter by source” dropdown menu.

Raw voter files can also be obtained from county Boards of Elections or similar offices, or the state. Commercial voter file data is available for purchase from a handful of organizations, such as L2 and others.

Do you have more questions?

Our help desk team can answer your questions about redistricting data and the redistricting process. Send a message and they will respond within one buisness day!