States redistrict their legislative and congressional districts once every 10 years using data from the decennial census conducted by the U.S. Census Bureau.
The bureau’s longstanding practice is to count persons incarcerated in state and federal correctional facilities as residents of the district where they are confined. The majority of states use the population and residence data reported in the census, as is.
Several states have changed their procedures for allocating inmate data for redistricting purposes. In these states, when possible, they reallocate data on inmatates in the redistricting data file from where they are incarcerated to their residence prior to incarceration.
The rationale behind this policy is that including incarcerated persons in the population count for the district in which their facility is located alters representational proportions and, as a result, the voting power of residents. Without reallocation, the total population of prison districts will contain fewer eligible voters (because prisoners can’t vote in most states), and thus the elected representatives for those districts represent fewer voters than their colleagues in parts of the state whose districts don’t contain prisons.
Implementing this policy often requires a significant amount of work and collaboration between agencies and authorities at the state and local level. For all affected incarcerated persons, accurate information on their residences immediately prior to their incarceration must be collected and recorded for later use by the appropriate redistricting authorities. The state’s census blocks as reported by the U.S. Census Bureau must also be updated based on this new data in order to reflect the correct populations pursuant to the state’s new apportionment procedures.
To date, 14 states have passed laws or adopted guidance modifying how incarcerated persons are counted and allocated during the redistricting process, although Illinois' law goes into effect for the 2030 cycle. States vary in their reallocation treatment of state and federal inmates and in their specific procedures for identifying and reporting incarcerated persons’ last known residences for redistricting purposes.
The table below provides a list of states that have passed laws modifying their redistricting procedures for incarcerated persons. It includes statute citations, the years enacted and implemented, whether the policy affect only legislative or congressional districts or both, and the specific treatment of both state and federal inmates.