Gerrymandering and GIS – problem or solution?


Ohio’s 2012-2022 Congressional Districts  (Ohio Secretary of State)

Gerrymandering, the process of manipulating political district boundaries for some advantage, is a broadly recognized but poorly understood process. This topic was first discussed here in GIS & You by Dennis Higgins in a September 2017 article. Now, Mark Salling, Ph.D., GISP, Senior Fellow and Research Associate at the Maxine Goodman Levin College of Urban Affairs at Cleveland State University, has written an informative article titled “Boundaries that matter: Partisan Gerrymandering of U.S. Congressional Districts” in the GIS Professional, the bimonthly newsletter of the Urban and Regional Information Systems Association.

The “one person, one vote” principle in the Equal Protection Clause of the Fourteenth Amendment to the U.S. Constitution requires that legislative districts must be very close in population to each other so that each citizen’s voting power is about the same. Who could argue with that? The First Amendment principles of free speech and expressive association also apply to voting when the drawing of political boundaries discriminates against certain viewpoints. Complicating matters, the Voting Rights Act of 1965 requires that the distribution of minority racial groups should be considered when drawing voting boundaries. As of 2015, there were 122 U.S. congressional districts where minorities composed a majority of the population.

Dr. Salling’s article discusses the question of who draws the district boundary maps after each decennial census. A very few states, including Washington, mandate that a non-partisan commission draw political district boundaries with limited direct participation by elected officials. But in the vast majority of states, the legislature draws the boundaries. This matters, because boundaries can be drawn to favor one party over the other, not just for U.S. congressional districts but also state legislative districts.

Dr. Salling focuses on an analysis of voting in Ohio for congressional district seats from 2002 through 2016. He demonstrates that for many elections, the percentage of seats won by the party that controls the drawing of political districts can be significantly higher than the percentage of votes cast statewide for that party.


One analysis relevant to compliance with the principles of fairness and one person, one vote in Ohio. (Salling)

GIS is a powerful tool that is used for creating political district scenarios and analyzing the demographic composition of each district. This has the potential to allow a political party that controls the process to create gerrymandered districts that maximizes the efficiency of their likely voters. Dr. Salling outlines ways that GIS and demographic data in the hands citizens or political watchdog groups can hold political parties to account when they create districts that do not comply with principles of competitiveness and fairness, or which fragment communities.

The Washington State Redistricting Commission has published rules for drawing the boundaries of the state’s 10 U.S. congressional and 49 state legislative districts. Those rules state:


Washington State congressional districts (Wikimedia Commons)

  • Districts shall have nearly equal population.
  • District lines should coincide with local political subdivisions (such as city and county lines) and “communities of interest.”
  • Districts should be convenient, contiguous (share a common land border or transportation route), and compact.
  • Districts must not favor or discriminate against one political party or group.
  • District divisions should encourage electoral competition.

Want to try your hand at redistricting by yourself or with family and friends? Download the Washington State Redistricting Board Game!

By the way, every 10 years, in preparation for the US Decennial Census, states, counties, and tribes across the country are invited to participate in LUCA – the Local Update of Census Addresses Operation. King County GIS is helping King County with its participation in the 2020 LUCA program. This program helps to create the most accurate census count possible for communities that participate. And of course this year the U.S. Census Bureau has a LUCA 2020 web map which shows agencies that are registered to participate.

Greg Babinski is KCGIS Center Marketing and Business Development Manager.

One thought on “Gerrymandering and GIS – problem or solution?

  1. Pingback: NSGIC publishes best practices guidance to improve elections with GIS | GIS & You

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