Illinois' congressional map drawing does not need to be contentious

  • Sheldon H. Jacobson

    Sheldon H. Jacobson

By Sheldon H. Jacobson
Guest columnist
Updated 8/16/2021 1:54 PM

The Census Bureau has released detailed census data that will permit every state to redraw their congressional maps. Illinois' decrease in population since 2010 means that it will lose one congressional district, moving from 18 to 17 representatives.

The Illinois mapping process is highly partisan, with a Democrat-led committee pulling the mapping strings. This is what occurred on Friday, June 4, when the governor signed the proposed State House and Senate maps into law. Republican lawmakers called foul, arguing that the data used to draw such maps were incomplete, based on the Census Bureau American Community Survey. What they were really upset about is their limited input into the process, and their inability to draw maps that favored their candidates.


Illinois is a strong Democrat-leaning state. If the Illinois map drawers gave Republican lawmakers carte blanche in drawing the Illinois state House and Senate maps, the Democrats would still end up with comfortable majorities in both chambers. This is just the nature of the state's political demographic landscape today.

The stakes for drawing the congressional maps are much higher, given that control of the House provides key national leadership positions for the majority party (not to mention nicer suites and facilities on Capitol Hill).

It is not always easy to identify a fair map, because there are so many ways to assess fairness. However, metrics exists to identify maps that have characteristics that make them highly unlikely to be fair.

Why should lawmakers want to draw maps that avoid such characteristics?

Creating maps that serve the voters is in everyone's best interest. When lawmakers intentionally gerrymander maps in their favor, it threatens the very foundations of our democracy. A disengaged population of voters serves no one's interest.

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The Illinois Constitution and federal law place few constraints on map drawing. In general, districts should have close to the same population and the Voting Rights Act must be satisfied with a number of majority-minority districts. After that, anything goes. Other desirable properties, though not mandated, include connectivity, compactness, and preserving communities of interest.

Instead of waiting for lawmakers to draw maps, why not give the voters in Illinois a glimpse of possibilities that will serve them well.

Our research group created several Illinois congressional maps, scoring them based on well-accepted fairness measures, like compactness, partisan asymmetry, efficiency gaps, and competitiveness. We used the Census Bureau American Community Survey as input data into our maps. Each of these measures is flawed of itself, but collectively, they provide an assessment of how well a map will serve the voters when electing their representative.

Anyone can access these maps, all created algorithmically. Our report, "Illinois Congressional Redistricting for 2021" contains 15 maps based on optimizing the fairness measures listed above.

We found that no one map scores well across all the fairness measures. The maps had between three and four majority minority districts, to satisfy the Voting Rights Act. We have intentionally not discussed the likely number of districts that each party will win in the upcoming midterm election, since anticipated outcome of elections should not be a factor to assess fairness. We found that across the 12 maps, the likely outcome in an election would give the Democrats between 10 and 12 Representatives.


With the Census Bureau now releasing the official census block data, our maps will be updated in the near future, though it is unlikely that the scores and map designs will be substantially different.

Map drawing does not need to be a political process. The people making it into one are the very people who have the most significant conflicts of interest in the process. This is why an independent commission with no current or former politicians should be involved in the mapping process. Anything less than this calls into question the ethics of the very people we entrust to run our government.

• Sheldon H. Jacobson, Ph.D., is a professor of computer science at the University of Illinois at Urbana-Champaign. His research group on computational redistricting is committed to bringing transparency to the redistricting process using optimization algorithms and artificial intelligence.

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