May 04, 2011 05:10 AM UTC

Comparison of Redistricting maps by the numbers.

•  
• by: Dan Willis

I said earlier today I would work on a report about the introduced Dem map. In the meantime, the GOP map has been introduced as well. See below the jump for a side by side comparison.

First of all, let me explain how I am evaluating the maps.

Each map when introduced includes a spreadsheet of how the vote came in in each of the new proposed districts for 3 past races: the US Senate race in 2010 and in 2008 and the CU Regent at large race in 2010.

The thought behind using these 3 races is to use a big race from each of the “wave” years. 2010 saw a surge in GOP participation and 2008 saw a similar surge on the Dem side. I guess they also included to the CU Regent race because it is lower profile and therefore likely to be a better barometer of more purely partisan voting, where US Senate is likely to include more “voting for the person” mentality.

I would have picked a slightly different set of races for this purpose to try to get to a more neutral guage of party strenth in a district, but no one asked me so I will continue with the same premise they are using.

When you average together the percentage results of each of the 3 races, then subtract the GOP result from the Dem result (or vise versa to guage GOP strength) you are left with a number that is called the Democratic Performance Index or DPI. (Republicans would go the other way and get a RPI). For example a district with a DPI of -3.53 means in a race between two exactly equal candidates, it could be expected to produce the result of the Republican winning by 3.53 percentage points. Of course, nothing is ever that cut and dry, but it is a reasonably accurate measuring tool as long as it is applied consistently.

Here is the DPI for each of the districts on the maps introduced. I am including one for the current districts for the sole purpose of giving you a feeling for how DPI’s relate to actual districts.

CD1:

Current: +45.06

SB268 (Dem map): +37.43

HB1319 (GOP Map): +39.39

CD2:

Current: +30.7

SB268: +10.46

HB1319: +15.9

CD3:

Current: +7.5

SB268: -13.67

HB1319: -4.33

CD4:

Current: -4.1

SB268: -7.47

HB1319: -8.44

CD5:

Current: -34.68

SB268: -22.66

HB1319: -28.04

CD6:

Current: -22.26

SB268: +5.67

HB1319: -10.06

CD7:

Current: +4.94

SB268: +4.64

HB1319: +3.97

So we can see the only place the two plans have a major conflict in terms of sheer numbers in CD6. Both plans have about the same degree of competiveness except that one district. In fact, the GOP has a more cometitive CD3 than the Dems.