On Dec. 20, the Census Bureau released its population estimates for 2017 for every state, detailing how many residents each state has gained or lost since the 2010 census. The firm Election Data Services has used these estimates to project how many congressional seats each state might gain or lose in the 2020 round of reapportionment, which assigns each state its share of the House’s 435 districts based on its population.
As shown in the map above (see here for a larger version), approximately 14 to 17 states might see their number of districts change after the 2020 census. The precise numbers vary because EDS offers two different projections, one based on longer-term population trends from 2010 through 2017 trends and the other based on the much shorter-term trend from just 2016 to 2017. A third projection relying on just the 2014 to 2017 trend yields the same result as using 2010 through 2017.
The 2020 census and subsequent reapportionment will thus set the stage for congressional redistricting. However, it’s difficult to predict with much accuracy what the partisan impact of these changes will be because we don’t yet know which party (if any) will control the redistricting process in many states.
The 2018 gubernatorial elections and legislative contests over the next three years will be critical for determining the partisan control over the process after 2020, and there are also two major upcoming Supreme Court cases that could place judicial limits on partisan gerrymandering. One thing we do know, however, is that much of the population growth in Sun Belt states like Texas comes from black, Latino, and Asian-American residents, which could benefit Democrats in those states.
Reapportionment will also determine how many Electoral College votes each state receives, since each state gets electoral votes equivalent to the number of House seats it has plus two for its Senate delegation. Adjusting the 2016 Electoral College outcome based on the above projections, Donald Trump would have gained two, while Hillary Clinton would have lost two, not nearly enough to affect the outcome.
Interestingly, the largely Midwestern and Northeastern states that are projected to lose seats almost all trended Republican in 2016, while the mostly Sun Belt states forecast to gain seats almost all trended Democratic. These trends could benefit Democrats in the long term if they can start winning regularly in places like Arizona, Florida, and North Carolina, even if Republicans shift toward a greater reliance on the Rust Belt.
This story has been updated to reflect newer data from Election Data Services. The updated forecast no longer has California losing a seats in one of the projections. Illinois loses just one seat in both projections instead of losing two in one forecast. Minnesota loses one seat in both projections instead of possibly seeing no change in one projection. Texas gains either two or three seats instead of both forecasts projecting three seats.
