Final answer:
Legislative redistricting in Illinois occurs every ten years following the U.S. Census, ensuring districts have approximately equal populations. The process aims to uphold fair representation and complies with federal laws and Supreme Court rulings. Some states use independent commissions for redistricting to reduce partisanship.
Step-by-step explanation:
In Illinois, legislative redistricting must be done every ten years. This process of redrawing district boundaries is required to ensure that each district maintains roughly equal populations and complies with the 'one-person-one-vote' principle established by the Supreme Court in Reynolds v. Simms (1964). The redistribution is usually based on the latest demographic information from the U.S. Census, which takes place every decade. As populations grow or decline, redistricting also accommodates changes in the number of districts within a state, although the total number of U.S. House seats remains at 435.
Redistricting can be a partisan issue, and in some cases, independent commissions, rather than legislators, are tasked with redrawing the electoral maps. The Supreme Court has upheld the use of these commissions, such as in the case of Arizona State Legislature v. Arizona Independent Redistricting Commission (2015).
Overall, the redistricting cycle seeks to balance representation and prevent malapportionment, which can result from shifting populations.