Congressional districts: How “equal” are they?

Congressional redistricting is the process of delineating boundaries for districts in which voters elect members to the United States (U.S.) House of Representatives. Currently, state legislative bodies and committees may consider up to eight criteria when determining the boundaries of districts and this paper focuses on one of those criteria, equal population. Congressional districts (CDs) are drawn to provide quality representation for a large population and are often redrawn due to changes in population reflected by the decennial census. The U.S. Supreme Court recently decided that equal population refers to the total population of a state, rather than any subgroups (e.g. registered voters, voting eligible population) but did not dictate that states could not evenly distribute any subgroups as well. This paper discusses how eligible voters may be defined and their distributions in each state for the 113th Congress. States with a large proportion of children or prisoners were expected to have CDs with eligible voting populations deviated from the equal population counts, but the results show that populations of children and prisoners were not significant factors related to the deviations from equal population counts at the state level. However, the changes in population between 2000 and 2010, and the non-citizen and Hispanic populations were strongly and significantly associated with the deviations from the ideals.