Following the decennial Census, political districts, such as U.S. Congressional Districts and state legislative districts, are reapportioned to states and counties on the basis of population and their boundaries are redrawn in a process called redistricting. Broadly speaking, the goal of redistricting is to make each district as close in population size in possible.
North Carolina is not the only state with uneven patterns of population growth. Across the United States, population is increasingly concentrated in urban and suburban areas. While most states have seen population growth since the 2010 census, more than half of all U.S. counties (53%) lost population between 2010 and 2014.
As a consequence of these uneven population changes, many congressional districts were already over or under ideal district size in 2014, in spite of the best efforts of individuals involved in state redistricting to ensure equal population during the 2011 redistricting process. If the experience of other states is similar to North Carolina’s, it is likely that these patterns of uneven growth will intensify through 2020, necessitating significant changes to legislative maps during redistricting in 2021. These changes will be required whether or not state representation changes during the reapportionment of seats in the House of Representatives.
Annual population estimates for U.S. Congressional Districts are available through the U.S. Census Bureau’s American Community Survey (ACS). The most recently available year is 2014.
North Carolina’s newly drawn districts are not currently provided in the ACS data. 2014 population estimates for these districts are available here.
Ideal population size is equal population across districts within a given state. Given the fixed number of seats in the House of Representatives (435), a growing national population, disparities across states in population size, “there will inevitably be population deviations in district sizes among states.”
Seven states have one seat in the U.S. House of Representatives—Alaska, Delaware, Montana, North Dakota, South Dakota, Vermont, and Wyoming. The 2014 population of these states ranged from 584,153 in Wyoming to 1,023,579 in Montana, meaning that Montana’s representative served 75% more constituents than Wyoming’s.
Among the states with more than one seat in the House, ideal district size in 2014 ranged from 527,587 in Rhode Island (2 seats) to 817,232 in Idaho (2 seats).
In 2014, the smallest district was Rhode Island’s 2nd congressional district, with a population of 523,028. Montana’s single congressional district was the largest, with a population of more than 1 million.
Although most districts were nearly perfectly equal in 2010, disparate growth patterns have already caused most districts to deviate significantly from ideal population size as of 2014. Because the redistricting process requires nearly perfect equality, with only small deviations (no more than +/- 0.5%), we identify districts with populations more than 0.5% above or 0.5% below ideal size as being significantly deviant from equality.
Eleven of North Carolina’s 13 congressional districts (85%) deviated from ideal population size by more than 0.5% in either direction in 2014. Most states have similar patterns.
Among other states with more than one congressional district, 339 of 415 districts or 82% deviated significantly from ideal population size in 2014. One hundred and seventy-seven (43%) were 0.5% or more under ideal size; 166 or 40% were 0.5% or more over ideal size.
In eleven states, every congressional district deviated significantly from ideal size. These states were Alabama, Arkansas, Georgia, Idaho, Kansas, Maine, Nebraska, New Mexico, Oregon, Rhode Island, and Utah. Only two states—Hawaii and New Hampshire, each with 2 congressional districts—had congressional districts that were still roughly equal in population in 2014.
Redistricting must be done using the decennial census counts. Using these counts, districts are made to be nearly as equal as possible within a state. State populations are continuously changing, however, and these changes rarely occur evenly across communities within a state. Consequently, congressional districts can quickly move away from equal population, as some communities grow slowly or lose population and other communities grow more quickly. These changes often necessitate significant boundary shifts during the next redistricting process, regardless of whether states lose or gain seats in the House of Representatives during reapportionment.