In Electionlawblog, posted by Nicholas Stephanopoulos

Historically, the general public has had no access to accurate partisan information about district plans. The operatives who painstakingly design the plans have had such information, of course. But members of the opposing party, journalists, activists, and ordinary citizens have either had no partisan data at all, or, at best, estimates based on disaggregating and reaggregating presidential votes. These estimates are useful, but presidential votes aren’t identical to legislative votes and don’t incorporate a factor, incumbency, that inevitably affects legislative votes.

To remedy this situation, PlanScore has just launched its Score a Plan feature. Users can now upload a district map at any level (congressional, state senate, or state house) for any of twelve states (Florida, Georgia, Illinois, Maryland, Massachusetts, Michigan, North Carolina, Pennsylvania, Tennessee, Texas, Virginia, or Wisconsin). Users can also specify whether each district has a Democratic incumbent, a Republican incumbent, or no incumbent. The site then instantly returns a detailed analysis of the map’s partisan characteristics. This analysis includes substantial information about each district as well as plan-wide scores like the efficiency gap, partisan bias, and the mean-median difference.

As a (nonrandom) example, here is PlanScore’s analysis of the current Wisconsin state house plan, assuming all open seats. The plan has a 12% pro-Republican efficiency gap, a 12% pro-Republican partisan bias, and a 4% pro-Republican mean-median difference. All these scores are very large by historical standards (as the below histograms indicate). The plan would also remain highly skewed in a Republican direction under a wide range of electoral conditions (as shown by the below sensitivity testing).

Read the full article here.