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Incumbent Addresses

This article discusses what incumbent address data is, what it is used for, who collected it, what is included in the data, how it was collected and processed, and how it can be accessed on the Redistricting Data Hub website.


Incumbent address data contains information about where incumbents live. The data are a critical tool for detecting incumbent gerrymandering in redistricting plans. States have different rules regarding if and how these data can be used in the redistricting process.

What are incumbent address data?

The incumbent address dataset contains information about incumbents, including their name, party affiliation, home address, GEOID, and the geographic coordinates (latitude and longitude) of their home address. It also contains demographic information including gender, race, ethnicity, and age. The data are available as a CSV or shapefile for state legislative and congressional incumbents based on the 2020 elections.

What are incumbent address data used for?

Incumbent addresses are a crucial tool for identifying incumbent gerrymandering because they can be used to determine whether redistricting plans have been drawn to favor or disfavor a particular incumbent. A few examples of this are placing an incumbent’s residence in or out of a particular district, drawing favorable constituents into a district, and drawing constituents that are likely to vote against the incumbent out of a district. Redistricting plans can also be evaluated using incumbent address data to see if the location of incumbents’ homes were favored over other criteria required by the state.

Some states explicitly prohibit using incumbent data when redistricting. For example, California does not allow the use of the place of residence of any incumbent or candidate in drawing maps. In the past, however, some redistricting committees and courts have required maps to avoid incumbent pairing or otherwise consider incumbent data.

Based on 2020 election results, the reelection rate for incumbents in the US House of Representatives was 96%, and state legislative incumbents had a 95% win rate. This high rate is due to a number of factors such as increased name recognition, access to campaign funding, and a proven track record for voters to reference. But it is also influenced by maps drawn to favor existing representatives. Incumbent gerrymanders in the redistricting process result in a democracy that is less responsive to voters, and these data can help identify when it has occured.

Who collected the data?

The incumbent address data available from the RDH was collected by Dr. Carl Klarner, a former political science professor specializing in election data with whom we contracted for these data.

Who is included in the data?

The data includes state legislators and members of the US House of Representatives elected on November 3, 2020. There are a total of 7,361 addresses for state legislators across all states. We received and verified updated addresses for four legislators in Colorado in the spring of 2021. This means that any other changes to incumbent data (i.e. through special elections) since 2020 are not incorporated in this data. For more information on incumbent changes since 2020, look for special elections on Ballotpedia.

How are the data collected and processed?

Dr. Klarner used the State Legislative Election Returns database to find the names of winners of state legislative general elections. For legislative chambers that had seats filled by general elections before November, 2020, legislators’ names were compared to lists of current legislators on state legislative websites. He then used a multi-step coding process to match incumbents’ names in the L2 voter file database to find and check addresses.

First, he matched legislator last names based on state legislative districts. In many cases there were multiple people in a given legislative district with the same last name as legislators. He narrowed down the results by matching first name and middle name, given the existing match on suffixes and legislative districts. However, some legislators go by their middle name, and their legal name is often unavailable. As a result, he marked registrants in the voter file as possible matches with the legislator if their middle name matched the listed first name of a legislator. He went through possible matches and checked with other information such as the legislator’s age or their spouse’s name to be sure that he selected the correct match. Any match failures that remained were dealt with individually.

He then used the Social Security Administration first name database to select a gender for legislators who had first names that were associated with one gender or another for over 99% of people in the database. For legislators who had names that could not be coded using this method, he used pictures of legislators to guess their gender. He also checked legislators’ gender against the voter file database. Lastly, he compared gender to the list of women legislators from the Center for American Women and Politics (CAWP).

He also coded the race/ethnicity of legislators. In a first round of matching, he based each categorization on surname (from the State Legislative Election Returns database) and pictures. He compared this to known Black and Latino legislators from Governing magazine as well as to race records for women legislators from the Center for American Women and Politics (CAWP). Race records from CAWP come from legislators’ self-identified race. Discrepancies between the original code, the Governing data, and the CAWP were manually reviewed and resolved. Lastly, he double-checked his coding, by using Census data to confirm whether over 50% of people with each surname were nonwhite. If a legislator with that surname wasn’t coded with that race, they were reviewed once more by cross-checking again.

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

Incumbent addresses can be downloaded from the Redistricting Data Hub website upon request only.

Fill out the request form and view the metadata on the dataset pages (download data > state > state or house incumbent address dataset)

Why is access to the data restricted?

Information about where legislators live is sensitive information. In order to protect the safety of all legislators to the extent possible, the RDH has restricted access to only those for whom we can verify the requestor’s identity, and their intended use of the data complies with our terms and conditions.

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!