Redistricting with 2020 Population Estimates (and 2016/2018 Political Data)

[Nyvin]

I would like to see Iowa in particular, because there is a relatively high chance in Iowa compared to other states that someone could put together what ends up being the real map (or at least extremely close to the real map) using these estimates.

Here's what I made with 2017 estimates:



2012-2016 pvi's:

IA-1(Blue): R+3.28
IA-2(Green): D+4.78
IA-3(Purple): D+2.35
IA-4(Red): R+13.88

Really shows just how empty the western half of the state is without the Des Moines metro.  Also shows how "urban packing" can actually work to the Democrat's advantage in Iowa if the same principal is applied here in R gerrymandered states.

Here's the district's populations by 2017 estimates, obviously 1 is overpopulated and 3 is under populated (should be 786,428 per district), but the only real way to correct it would be a county split, which would mess up the estimates.

IA-1
TOTAL   793860
   
IA-2   
TOTAL   786530
   
IA-3   
TOTAL   776994
   
IA-4   
TOTAL   788884


https://factfinder.census.gov/faces/tableservices/jsf/pages/productview.xhtml?src=bkmk

[Nyvin]

I like this map, but IA-02 would probably violate their rules on compact districts.

Good point,  convinced me to redo it.

Here's a much improved version, aside from splitting up Linn and Johnson counties (yuck!).



2012-2016 PVI

IA-1: D+0.6
IA-2: D+1.26
IA-3: D+1.8
IA-4: R+13.88

District populations by 2017 estimates:

IA-1: 790699
IA-2: 780008
IA-3: 786801
IA-4: 788884

Tama County can be split to even out the populations of IA-1 and IA-2.  I don't think it gets much better than this for compactness.   Three swing seats too.

[Nyvin]

OK, I did Iowa. The original post is updated with a link to the Iowa 2020 population estimates DRA file. If you want to try using the data, as with the Virginia data you just need to download the file and overwrite your existing file in your Iowa DRA folder.



Here is a possible map using the 2020 estimates for Iowa which does not split any counties. It is pretty similar to the map Nyvin posted, but IA-01 an IA-02 are more compact. The population deviations are -249, 1865, -1841, and 226. You may be able to get the deviations down further without splitting counties with some alternative configurations, but the deviations are clearly well within the error of the estimates.



Since Iowa likes to avoid splitting counties, very slight error between population projections and the actual 2020 census data could lead to a significantly different map. But it does seem like it may be possible to have a neat compact Des Moines area map, 2 fairly compact districts in the east, and 1 in the west.

Iowa is another state where Republicans tend to be self-packed in the western part of the state. So it is pretty much inevitable that IA-04 will in some form or other be safe R, and the other 3 districts swing districts to some extent or other, unless maybe IA-04 is re-oriented in the northern part of the state instead of the west.

IA-01 is D + 0.4
IA-02 is D + 0.8
IA-03 is D + 2.3
IA-04 is R + 13.3

This look pretty good!   Your map pretty much confirms to me that it's near impossible to have a compact map and keep Linn and Johnson counties in the same district, lol.

[Nyvin]

This look pretty good!   Your map pretty much confirms to me that it's near impossible to have a compact map and keep Linn and Johnson counties in the same district, lol.

This seems to be about the best that can be managed while keeping Johnson and Linn together. But it has a population deviation of a bit more than 2000 on IA-04, and Linn county is sticking out awkwardly.

Nice,  what are the PVI's for that?  It looks like the map the Republicans would push for since it creates somewhat of a Dem Pack in the southeast district.