Legislative districts vary in size primarily because of population changes, legal requirements, and redistricting principles. Districts are drawn to have roughly equal populations to ensure equal representation, but population growth is not uniform across areas, which causes size variation. States redraw district boundaries after each census to adjust for these population shifts, but some latitude is allowed for factors like keeping political boundaries intact or geographic compactness, especially in state legislative districts. Larger deviations can occur due to political motivations or specific legal allowances.
Reasons for Variation in District Size
- Population Changes: Districts represent population groups, and as population grows unevenly across areas, districts need to be adjusted to maintain equal representation. Some districts grow larger in area when population is sparse, and smaller in area where population is dense.
- Legal Requirements: The U.S. Supreme Court mandates congressional districts to have nearly equal populations to provide equal representation ("one person, one vote"). State legislative districts usually allow a small variation margin (up to about 10%) to respect political boundaries or practical considerations.
- Redistricting Practices: After each U.S. Census, district lines are redrawn to balance populations. The process considers multiple factors like population equality, compactness, community integrity, and sometimes political advantage, leading to variations in district sizes.
- Geographic and Political Considerations: In rural areas with low population density, districts may cover a larger land area to encompass enough residents. Conversely, urban districts are geographically smaller but more densely populated. Political interests and historic district boundaries can also influence district size differences.
Summary
Legislative districts vary in size because they aim to represent approximately equal populations, but population distributions, legal allowances, and political or geographic considerations cause differences in both physical size and population deviations among districts. The redistricting process tries to balance these competing factors following each census. This leads to districts varying in both geographic area and population within legal limits, reflecting how populations shift and how districting rules are applied.
