More on gerrymandering

 I have done some analysis on the variance between the popular vote vs. seats held in a legislative body for a few states across the 2018 and 2016 elections.  I've tries to find if I can download the data in some format and while some of the states do provide some files that can be downloaded, it has been easier to create a spreadsheet and enter the values myself.  As a result it is rather slow to develop the data, but already, for comparison I have found a few interesting results.  See the graph below (made with matplotlib, let me know if you are interested in the code).  This plots a number of elections with the Kg coefficient that I have calculated on the x-axis and the number of seats in the legislature on the vertical axis.  For the state senates, I have used the number of seats in the senate even though generally only half the seats are up in any general election.  Then I plotted 2 lines.  The green line is where the marker would be if the overall Kg reflected a variance of 1 seat between the popular vote and the seats held.  The yellow line is where the marker would be if the Kg reflected a variance of 2 seats.

Some of the interesting things that we see here is that most legislative bodies seem to reflect some bias.  This does not identify which party benefits.  It just identifies if there is a bias.  Some bodies do have a pretty high level of bias.  For a number of these bodies I included a point for 2016 as well as 2018.  The direction of change cannot be predicted and seems to be a function of what motivates voters to go vote more than a function of the map.  While setting up a map overall can tilt the playing field, judging on the change in Kg from election to election, shows that migration, candidate quality and voter motivation can all influence the results, for example note the movement of the Idaho Senate and House between 2016 and 2018.  One moved in the direction of more gerrymandering and the other in the direction of less.  In compiling the statistics, I was struck by how many districts (about 20%) only had a single candidate.  This kind of situation clearly depresses voting based on the results that were reviewed.  In a district where there were multiple candidates, the number of votes cast was in some cases double.  For example, in Oregon, when there was only 1 candidate the number of "other" votes, typically write-ins and possibly spoilt ballots, was 10 times when a candidate from both the democratic and republican parties was on the ballot.

The next thing I am going to investigate is the change over time of the Oregon House and Senate, especially if I can see if there was a marked change as a result of the decennial redistricting.