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The Illinois remapping committee revealed its proposed new congressional map. What it did not reveal are some of the key metrics that illuminate how gerrymandered it is.

The committee was highly effective in packing Republican-leaning downstate voters into districts 12, 15 and 16. It is conceivable that they will be the only three districts that the Republican candidates will win, as many have already noted.

Of the remaining 14 districts, six are certain to be Democrat wins and eight will be competitive, with all leaning to Democrats, based on Illinois election results over the past four years.

The eye test alone suggests that the maps were drawn with an objective of maximizing the number of Democrat candidates that can be elected to Congress. For example, District 17 stretches from Rockford in the north down to Bloomington in central Illinois, grabbing Moline and Peoria, while avoiding the rural area directly between Rockford and Peoria. The goal is for this district to lean Democrat by cracking the rural voters who tend to vote Republican.

District 15 covers over one-half of the north-south height of Illinois, snaking through rural areas to avoid any downstate Democrat-leaning urban areas, to pack Republican voters together.

District 13 is particularly revealing. It looks similar to the current District 13. However, the committee carefully crafted it to grab as many urban voters and college towns as possible, stretching all the way from Champaign-Urbana down to the Democrat-leaning St. Louis suburbs.

It also breaks the Decatur area up into two districts, and excludes Mahomet from the Champaign-Urbana area. Lastly, it excludes Taylorville, the home of Rodney Davis, the current Congressman in the district.

So the map fails the eye test. But what do the analytics say about the map?

Our University of Illinois at Urbana-Champaign research group compiled a report to provide Illinois voters with an analytical analysis of key features of the proposed map.


  • The eye test suggests no compactness, and the analytics support it. The total perimeter length of the 17 districts is close to 11,000 miles.

In contrast, our research group created several maps with total perimeter lengths of around 6,000 miles.

Efficiency Gap:

  • This measures the relative proportion of wasted votes (votes cast that do not contribute to winning a district or are in excess of the 50 percent needed to win a district) between the two parties.

The proposed map scored a disproportionate number of wasted Republican votes, scoring well beyond what would be reasonable and fair for voters.

Partisan Asymmetry:

  • This measures how shifts in voter support impact the distribution of seats won by each party. Ideally, if each party’s candidates saw a similar increase in voter support across the state, there would be a similar impact on districts won.

In this case, this measure is fairly balanced, indicating no extreme bias.


  • Eight of the 17 districts are competitive, as measured by the gap between the two-party candidates being within plus or minus 10 percent. Four of the districts are within five percent.

However, all the competitive districts lean Democrat.

The takeaway from this analysis is that the map proposed by the Illinois remapping committee is heavily gerrymandered in favor of the Democrat party. Given that Illinois is a 59 percent to 41 percent Democrat-Republican voting state, a 14-3 Democrat-Republican split in districts does not serve the state well.

It disenfranchises downstate and rural voters, giving them little representation. It also gives only Democrat representation to all the Chicago suburbs, which possess a significant proportion of Republican voters.

At the same time, the proposed map may be risky for Democrats. There are four districts (3, 6, 14, 17) that are sufficiently competitive that a grassroots “get out to vote” effort by Republicans may swing them. Even Districts 11 and 13 are within striking range for Republican candidates.

In a time when we need leaders to build bridges and provide support for all residents of Illinois, the proposed congressional map is divisive and does not represent the interests of all Illinois voters. It devalues voters, particularly those downstate, in rural areas, and in the Chicago suburbs.

That, unfortunately, is the message behind the proposed map.

“Illini-mandering” represents yet another example of partisan mapping. Is this my opinion? No. It is the assessment informed by analytics.

Sheldon H. Jacobson is a UI professor of computer science. 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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