Americans are increasingly divided by density, with rural areas leaning Republican and urban areas voting Democrat. But when it comes to the battle for Congress, congressional districts are tricky to categorize. Encompassing hundreds of thousands of residents each, they often contain cities, farmland, and suburbs in varying mixtures.
So CityLab came up with the Congressional Density Index: a way to classify all 435 congressional districts by their makeup of different types of neighborhoods. This isn’t just a curiosity—looking at the House through the lens of the Congressional Density Index showed that Republican difficulties in 2018 were concentrated in suburban districts long before the votes were cast.
Want to learn more? Here are some quick links:
- Read an introduction to the model and what it predicted for the 2018 elections
- See the full list of how each district was classified
- Explore how CityLab created the Congressional Density Index
Here’s the full list of CityLab articles using the Congressional Density Index:
- How the Suburbs Will Swing the Midterm Election
- In These Outlier Congressional Districts, Density Doesn’t Equal Democrats
- The 2010 Midterm Wave Rewrote America’s Political Geography. Will 2018 Do It Again?
- Density Will Affect Who Controls State Legislatures, Too
- Suburban Voters Gave Democrats Their House Majority
CityLab released the Congressional Density Index under the open-source MIT License and Creative Commons Attribution-ShareAlike 4.0 International License, which means anyone is free to use it provided you attribute CityLab and maintain this open license. A number of other analysts and publications have used the Congressional Density Index to explore the 2018 election, including the following articles:
- The Hill: “Suburban voters will decide control of Congress”
- Hawai’i Public Radio: “Justice Kavanaugh and the Upcoming 2018 Congressional Election”
- FiveThirtyEight: “Democrats Can Get Close To A House Majority With Suburban Seats Alone”
- FiveThirtyEight: “The Suburbs—All Kinds Of Suburbs—Delivered The House To Democrats”
- Axios: “Suburban districts moved toward Democrats in 2018”
- The Washington Post: “The shifts that handed the Democrats the House”
- Business Insider: “The diverging midterm results show there’s a growing political chasm in America. And both parties look like they’re digging in.”
Want to go deeper?
- Examine and download the computer code (in the R language) that CityLab used to create the Congressional Density Index
- Learn about some of the districts the model had a hard time classifying
- See classifications for the congressional districts used before the most recent round of redistricting in 2012