2021
\r\nA First Look at Post-2020 Redistricting
\r\n \r\nThe Center for Urban Research (CUR) at The Graduate Center of the City University of New York (CUNY) has created the Redistricting & You online map to help members of the public, journalists, elected officials, and other redistricting stakeholders to understand the local implications of redrawing legislative district lines across the country.
\r\n \r\nThe initial version of this website used population estimates, but as of August 2021 it has been updated with the official population counts from the 2020 Census to show several demographic characteristics that will help inform the redistricting debate.
\r\n \r\nMany factors will go into drawing new maps. A fundamental issue is how each district's population has changed since the last redistricting cycle. The 1 person, 1 vote principle says that legislative districts should have an equal number of people (congressional districts follow that principle strictly; state districts have more leeway).
\r\n \r\nBut populations have shifted and grown or declined in the last 10 years. Some districts now have many more people than the average district size; these districts will need to shrink. Other districts now have far fewer people than average; they will need to expand. CUR's Redistricting & You map highlights these patterns across the country to visualize how the districts may need to change.
\r\n \r\n \r\n\r\n\r\n\r\nData sources
\r\nCongressional district population
\r\nThe default view of the Redistricting & You map shows the difference from average (sometimes referred to as \"ideal\") district population by state for congressional districts. The average congressional district population for each state is calculated by dividing state population by reapportionment district counts for each state.
\r\n\r\nAs of August 2021, our map uses the 2020 Census data for congressional district and statewide population.
\r\n\r\nState legislative district population
\r\n\r\nFor state legislative districts, we divide each state's total population by the number of upper or lower house representatives (to account for multimember districts) in the corresponding state to determine average (or \"ideal\") legislative district population. We compare each upper and lower house district population (or average population for multimember districts) with the statewide average to calculate the difference for each district. The number of upper and lower house representatives in each state is based on the count of state representatives from the OpenStates API.
\r\n\r\nAs of August 2021, our map uses the 2020 Census data for state legislative district and statewide population.
\r\n\r\nPopulation caveats
\r\nNote that congressional districts are apportioned based on resident population plus overseas military population, while \"ideal\" congressional sizes are based on only resident population.
\r\n\r\nAlso, the 2020 Census data used for our map does not separately account for the population of incarcerated persons based on their last known residence; this population is included in the 2020 data based on where they are confined. For the purpose of redistricting, some states will reallocate prisoners from the prison location to their residence prior to incarceration.
\r\n\r\nRace/Hispanic origin
\r\nOur map uses 2020 Census data to show the distribution of population for each district by race/Hispanic origin categories (for total population and for \"voting age population\").
\r\n\r\n A separate map overlay (accessible via the legend in the bottom right corner of the map) displays predominant race/Hispanic origin patterns by tract based on the 2015-2019 American Community Survey estimates for \"citizen voting age population\" (CVAP).\r\n
\r\n\r\nVoting data
\r\nThe map overlay that shows vote share by precinct for the 2020 presidential election is from the New York Times 'extremely detailed map of the 2020 election.' More information about the data and its caveats is available here, and the MIT license for reusing the data is here.
\r\n\r\nDistrict population change over time
\r\n\r\nTo show population change over time, the map compares 2020 & 2010 population counts. In order to allocate 2010 population to current districts, we use the 2010 PL 94-171 data for all census blocks nationwide (downloaded via the Census Bureau API). We allocate those block population counts to current, 2020 census block geography using the Census Bureau's block relationship files, and then aggregate those allocated block counts by current districts using the Bureau's block assignment files.
\r\n\r\nDistrict boundaries & representative name/party
\r\n\r\nDistrict boundaries are displayed from the Census Bureau's TIGER files. With the exception of North Carolina, congressional district boundaries reflect the 116th Congress, and state district boundaries reflect districts as of 2018. This follows Census Bureau guidance that any legislative district boundary changes \"between the 2018 election and [the Bureau's] postcensal collection are not reflected in Census Bureau products\" until the 118th Congress and year 2022 state legislatures. In North Carolina, however, districts were redrawn in 2019, and our map reflects those redrawn districts. However, we have allocated 2010 and 2020 population counts to those new NC district boundaries.
\r\n\r\nFor each Congressional district and state legislative district, the map provides the representative's name from ProPublica's Congress API & the Open States API for state districts.
\r\n\r\nCredits
\r\nThe map application was developed by the CUNY Mapping Service at the City University of New York's Graduate Center. The Mapping Service, part of the Center for Urban Research, engages with foundations, government agencies, businesses, nonprofits, and other CUNY researchers to use spatial information and analysis techniques to develop and execute applied research projects.
\r\n\r\nThe Redistricting & You project is coordinated by Steven Romalewski. The Mapping Service's senior application architect Will Field designed, created, & coded the application. Valerie Bauer, a graduate of Lehman College's Geographic Information Science program, compiled and analyzed the data behind the map, and helped develop the map designs & color themes.
\r\n\r\nThe Center for Urban Research is a leader in applied research projects focused on demographic change, immigration trends, and neighborhood analysis. The Center is led by John Mollenkopf, distinguished professor of sociology and political science at The Graduate Center. Dr. Mollenkopf is helping to oversee the project.
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Funding support for the Redistricting & You map — especially the upcoming version focused on New York State to compare current districts with proposed maps — has been provided by the New York State Census Equity Fund, which was established in 2018 in The New York Community Trust to ensure coverage of the State's hard-to-count communities in the 2020 census and to extend community-based organizations' level of civic engagement into the redistricting process. More information on this and other collaborative funds at the Trust is available here.
\r\n\r\nThanks to the many people who provided feedback and suggestions for improvement based on early versions of the map. We encourage everyone using the map to send us feedback so we can continue to improve its usefulness. Thank you!
\r\n\r\nThe mapping website relies on the Graduate Center's server infrastructure and the support of the Graduate Center's information technology team.
\r\n\r\nThe application itself is built using a mix of open source and proprietary tools and technologies including:
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- \r\n Techniques and design components developed initially for the CUNY Census 2020 Hard to Count/Response Rate map;\r\n \r\n
- \r\n Mapbox, which is providing generous support hosting nationwide map layers that are featured on the map (the map uses MapboxGL.js, as well as static tiles for features such as place names, points of interest, and waterbodies);\r\n \r\n
- \r\n Google's places API powers the address/location search feature;\r\n \r\n
- \r\n several JavaScript libraries including Vue (enhanced with Vuetify), d3, and node; and\r\n \r\n
- \r\n all the data for the map is managed via Postgres and PostGIS, hosted via Amazon Web Services.\r\n \r\n
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