Illinois released draft state legislative district plans on Friday evening. Here’s PlanScore’s analysis of the state house map (hat tip to Brian Amos for converting the map into a usable digital format). It’s predicted to have a pro-Democratic efficiency gap of 2%. That’s somewhat more pro-Democratic than the existing state house plan, which had an average efficiency gap of 3% in a Republican direction from 2012 to 2018. But it’s still a low figure not indicative of a significant bias in either party’s favor.
Notably, Illinois’s draft state house map pairs this small efficiency gap with numerous noncompact districts, especially in and around Chicago. It’s likely that if the map’s districts were less oddly shaped, the map would be considerably more tilted toward Republicans. The map thus squarely presents the vexing issue of redistricting baselines. Is partisan symmetry the right benchmark? In that case, the map is exemplary since it should accurately translate the partisan preferences of Illinois voters into legislative seats. Or is the baseline what a redistricting process would produce if it ignored election results and prioritized nonpartisan criteria like compactness and respect for political subdivisions? If so, the map is probably skewed substantially in a Democratic direction (though further analysis would be necessary to prove that point).