Electoral District - Apportionment and Redistricting

Apportionment and Redistricting

Main articles: Apportionment and Redistricting

Apportionment is the process of allocating a number of representatives to different regions, such as states or provinces. Apportionment changes are often accompanied by redistricting, the redrawing of electoral district boundaries to accommodate the new number of representatives. This redrawing is necessary under single-member district systems, as each new representative requires their own district. Multi-member systems, however, vary depending on other rules. Ireland, for example, redraws its electoral districts after every census while Belgium uses its existing state boundaries for electoral districts and instead increases the number of representatives alloted to each.

Apportionment is generally done on the basis of population. Seats in the United States House of Representatives, for instance, are reapportioned to individual states every 10 years following a census, with some states that have grown in population gaining seats. The United States Senate, by contrast, is apportioned without regard to population; every state gets exactly two senators. Malapportionment occurs when voters are under or over-represented due to variation in district population.

Given the complexity of this process, software is increasingly used to simplify the task, while better supporting reproducible and more justifiable results.