US House Redistricting: Iowa

[muon2]

From the looks of it there are no easy ways to create a compact CD from only Polk County and eight counties around it that also produces very low deviation.

I've found arrangements with less than 100 deviation. One arrangement that included Polk and Dallas plus counties to the south had a deviation of 11.

[muon2]

From the looks of it there are no easy ways to create a compact CD from only Polk County and eight counties around it that also produces very low deviation.

Interesting how populous that area is now- if you added all eight counties, you’d be 100022 people over target.

The most compact/neat option is Polk, Dallas, Jasper, Marshall, Story, Boone (excluding the three at the bottom), which results in a district 2343 under.

If that’s not close enough to target, there’s a closer option. Polk, Dallas, Jasper, Story, Warren, Madison. This is 212 under, and it’s still a decent shape- the three counties not included are the northwest, northeast, and southeast corners of the eight. Wouldn’t surprise me if they go for that.

I don't think they will be concerned about those specific eight. They will try for 4 CDs that minimize deviation while remaining reasonably compact. Population equality is the priority, though it is not absolute. As I noted above they settled for a range of 76, since lower deviations were considerably less compact.

[muon2]

Here is my sample map using the new county data.


The district deviations are blue +26, yellow +55, red +11 and green -91 (rounded). The range is 146 with an average deviation of 45.62.

State law establishes the following criteria for both congressional and state legislative districts:[32]

   Districts must be "convenient and contiguous."
   Districts must "preserve the integrity of political subdivisions like counties and cities."
   Districts must "to the extent consistent with other requirements, [be] reasonably compact–defined in terms of regular polygons, comparisons of length and width, and overall boundary perimeter."

The comparison of length and width rule favors districts that fit in boxes of equal height and length, which is generally accomplished by all four districts. The shape of the yellow district doesn't look great, but the others are quite nice. The boundary between the yellow and blue districts is what creates the poor shape, but it isn't extreme in terms of its length. Since the plan is judged by the total perimeter of all districts, one weak district/boundary usually doesn't hurt the metric much.

I'm sure this isn't the optimal plan since it was only my second stab at it today. I'm curious to see other plans in the same or better population equality ranges.

[President Punxsutawney Phil]

From the looks of it there are no easy ways to create a compact CD from only Polk County and eight counties around it that also produces very low deviation.

I've found arrangements with less than 100 deviation. One arrangement that included Polk and Dallas plus counties to the south had a deviation of 11.

Interesting.

[Torie]

I plugged Muon2’s map into the DRA. It makes IA-03 about 70 basis points more Dem (Trump lost the existing version by 10 basis points, and this iteration by 1.3%. The movement is about the same in the 2020 Senate race. Ernst was hurt by a Libertarian candidate running however, who pulled 3%. That guy is interesting. We are the same age, and both got MBA’s at the University of Chicago. His views basically parrot those of Milton Friedman, perhaps having been exposed to them there. (I actually chatted with Friedman a few times, and drove with his son David to a Libertarian convention in Philadelphia. I bet he would be a bit envious if I told him about that about that.    But he went there about 18 years after me, after having made a bunch of money owning a business, so Milton Friedman was no longer in the hood. His favorite book is James Joyce’s Ulysses. Interesting guy, with an obviously high IQ.  Ulysses is not an easy book to read, trust me. https://ballotpedia.org/Rick_Stewart#Campaign_themes

https://davesredistricting.org/join/81d2fbbb-9206-4e10-9ae4-05088ec9363b

[Nyvin]

Here's a IA-3 with a deviation of 7, lol.

I think the IA-4 in this map is near perfect.   IA-1 and IA-2 are both pretty boxy too.

I don't know if the deviation on 1 and 2 is too high though.



https://davesredistricting.org/join/a91c340d-5ea3-4a40-bd8b-c830f11874c2

I think this is what I'd probably draw though -



https://davesredistricting.org/join/c35f45e2-2a4a-47c6-8115-eb98389e0b1f

[Thunder98 🇮🇱 🤝 🇵🇸]

Here's IA with the 2020 data. Probably the most favorable map for the GOP as I separate Johnson and Linn County into different districts to prevent making another toss-up/tilt D district.

https://davesredistricting.org/join/c6f2999e-c11b-4e1e-b821-58b8e0f583a8

[President Punxsutawney Phil]

Here's IA with the 2020 data. Probably the most favorable map for the GOP as I separate Johnson and Linn County into different districts to prevent making another toss-up/tilt D district.

https://davesredistricting.org/join/c6f2999e-c11b-4e1e-b821-58b8e0f583a8

Most GOP favorable map possible should probably have Iowa City and Des Moines in the same district.

[muon2]

Here's a IA-3 with a deviation of 7, lol.

I think the IA-4 in this map is near perfect.   IA-1 and IA-2 are both pretty boxy too.

I don't know if the deviation on 1 and 2 is too high though.



https://davesredistricting.org/join/a91c340d-5ea3-4a40-bd8b-c830f11874c2

I think this is what I'd probably draw though -



https://davesredistricting.org/join/c35f45e2-2a4a-47c6-8115-eb98389e0b1f

I like it. I hadn't started playing with a split of Polk and Dallas. West Des Moines and Urbandale are large suburbs and substantially in both counties. The team that follows state law (avoid city splits) to draw the maps may not want to go in that direction.

What are the deviations for all the CDs on both plans?

[Nyvin]

Here's a IA-3 with a deviation of 7, lol.

I think the IA-4 in this map is near perfect.   IA-1 and IA-2 are both pretty boxy too.

I don't know if the deviation on 1 and 2 is too high though.



https://davesredistricting.org/join/a91c340d-5ea3-4a40-bd8b-c830f11874c2

I think this is what I'd probably draw though -



https://davesredistricting.org/join/c35f45e2-2a4a-47c6-8115-eb98389e0b1f

I like it. I hadn't started playing with a split of Polk and Dallas. West Des Moines and Urbandale are large suburbs and substantially in both counties. The team that follows state law (avoid city splits) to draw the maps may not want to go in that direction.

What are the deviations for all the CDs on both plans?

Hmm...That's interesting about the Municipality splits.   Does this entail that Polk, Dallas, Warren, and Madison all end up in the same district?

First map deviations-
1
-1,900

2   
1,095

3   
 7

4   
799

Second Map-
1
196

2   
171

3   
344

4   
-710

[muon2]

Here's a IA-3 with a deviation of 7, lol.

I think the IA-4 in this map is near perfect.   IA-1 and IA-2 are both pretty boxy too.

I don't know if the deviation on 1 and 2 is too high though.



https://davesredistricting.org/join/a91c340d-5ea3-4a40-bd8b-c830f11874c2

I think this is what I'd probably draw though -



https://davesredistricting.org/join/c35f45e2-2a4a-47c6-8115-eb98389e0b1f

I like it. I hadn't started playing with a split of Polk and Dallas. West Des Moines and Urbandale are large suburbs and substantially in both counties. The team that follows state law (avoid city splits) to draw the maps may not want to go in that direction.

What are the deviations for all the CDs on both plans?

Hmm...That's interesting about the Municipality splits.   Does this entail that Polk, Dallas, Warren, and Madison all end up in the same district?

First map deviations-
1
-1,900

2   
1,095

3   
 7

4   
799

Second Map-
1
196

2   
171

3   
344

4   
-710

I don't think minor overlaps are as much of a concern as major ones. Keep in mind that each CD will have 25 nested House districts and they are paired to form Senate districts such that only two Senate districts will span CDs - one per pair of adjoining CDs. The minimize county and city split rules apply to the legislative districts, too, and the mappers build all the plans at once.

The legislature doesn't draw the maps, but they can vote them down with instruction as to the statutory criteria they felt weren't adequately met. So if the Pub legislature doesn't like the Polk - Dallas split they can send it back to the mappers with specific instructions to maintain city integrity.

I'm sure all the deviations will be considered too high. Last cycle the deviations were all less than 100. I did an analysis of Atlas submissions back in 2013 and found that one can reasonably predict the deviation one should be able to achieve in a whole county plan. I excerpted from the thread and put it in the Atlas WIKI. For 99 counties and 4 CDs that number is under 100, which is why I expect that there are more precise plans than the one I put up. I may play with your first plan to see how it might be improved for pop equality.

[Nyvin]

I kinda think aiming for zero population deviation is a rather useless effort.   It doesn't actually change the district in any meaningful way to add/subtract a few hundred people.

But that aside,  here's what I came up with,  I don't know if the IA-1 district's eastern arm would work though.





https://davesredistricting.org/join/c35f45e2-2a4a-47c6-8115-eb98389e0b1f

IA-1 with deviation of 1 and IA-3 with deviation of 2 isn't all that bad, lol.

[muon2]

I kinda think aiming for zero population deviation is a rather useless effort.   It doesn't actually change the district in any meaningful way to add/subtract a few hundred people.

But that aside,  here's what I came up with,  I don't know if the IA-1 district's eastern arm would work though.





https://davesredistricting.org/join/c35f45e2-2a4a-47c6-8115-eb98389e0b1f

IA-1 with deviation of 1 and IA-3 with deviation of 2 isn't all that bad, lol.

The issue is that SCOTUS allows for 0 population deviation for CDs. If there are other considerations then the population deviations must be lowest achievable given those considerations. I agree that deviations as large as a 1% range would be fine, especially since the population shifts between Apr 2020 and Nov 2022 are comparable to a few tenths of a percent deviation in most CDs. SCOTUS hasn't been convinced yet, but there are those observers who think that the current composition may be open to loosening the equality requirement.

BTW I found a nice safe compact Dem cluster (includes Johnson, Linn, Black Hawk and Dubuque) with a deviation of only 13! I put it with one of your earlier Polk clusters to get this plan. I wasn't able to get a sub 100 deviation when I put it with your new and improved Polk cluster.



The deviations are blue -13, yellow -48, red +7, green +55. The avg dev is 30.75 and the range is 103.

[walleye26]

This is kind of a dumb question, but I’m curious. It sounds like you guys are saying Iowa prohibits splitting counties. What happens when you have to? Like, let’s say for a second Polk county’s population goes to 890,000 next decade. You are going to have to split that. What then?

[BoiseBoy]

This is kind of a dumb question, but I’m curious. It sounds like you guys are saying Iowa prohibits splitting counties. What happens when you have to? Like, let’s say for a second Polk county’s population goes to 890,000 next decade. You are going to have to split that. What then?

Iowa splits counties for their state legislature districts. I imagine they'll just start splitting Polk when it gets to that point on the congressional level.

[Oryxslayer]

i doubt anyone can beat this (much less without insane shapes) https://twitter.com/corymccartan/status/1426562111447212032?s=21

Someone used a least-deviation algorithm to get this map, and since we don't have any 0-0-0-0 style maps yet it's hard to imagine it not coming up as one of the solutions by the official board. OTOH, I doubt the GOP goes for it cause that is a reliably 2-2 map with a Ames-Des Moines seat and a Cedar Rapids-Iowa City seat.

[Torie]

This is kind of a dumb question, but I’m curious. It sounds like you guys are saying Iowa prohibits splitting counties. What happens when you have to? Like, let’s say for a second Polk county’s population goes to 890,000 next decade. You are going to have to split that. What then?

Because Iowa has so many counties of about the same size in area so logically arranged, with so many having relatively small populations, that there is about a zero chance that it would be impossible to draw a plan that cannot both avoid splitting counties and keep below a 1% deviation which is the max allowed by SCOTUS.

[America Needs a 13-6 Progressive SCOTUS]

This is kind of a dumb question, but I’m curious. It sounds like you guys are saying Iowa prohibits splitting counties. What happens when you have to? Like, let’s say for a second Polk county’s population goes to 890,000 next decade. You are going to have to split that. What then?

Because Iowa has so many counties of about the same size in area so logically arranged, with so many having relatively small populations, that there is about a zero chance that it would be impossible to draw a plan that cannot both avoid splitting counties and keep below a 1% deviation which is the max allowed by SCOTUS.

You misread the post it seems, the question being asked was what would happen if a County was large enough on its own that it was bigger than the sum needed for a Congressional District all by itself.

[Torie]

This is kind of a dumb question, but I’m curious. It sounds like you guys are saying Iowa prohibits splitting counties. What happens when you have to? Like, let’s say for a second Polk county’s population goes to 890,000 next decade. You are going to have to split that. What then?

Because Iowa has so many counties of about the same size in area so logically arranged, with so many having relatively small populations, that there is about a zero chance that it would be impossible to draw a plan that cannot both avoid splitting counties and keep below a 1% deviation which is the max allowed by SCOTUS.

You misread the post it seems, the question being asked was what would happen if a County was large enough on its own that it was bigger than the sum needed for a Congressional District all by itself.

I did indeed. That won't happen for a long time, but if it does, Polk will have to be split. SCOTUS trumps all. Is that a better answer?

[Torie]

I tend to doubt that the Pubs will be willing to concede a rather safe seat for the Dems unless they have to. Does anyone disagree?

[America Needs a 13-6 Progressive SCOTUS]

I tend to doubt that the Pubs will be willing to concede a rather safe seat for the Dems unless they have to. Does anyone disagree?

Iowa is probably not Republican enough for a 4-0 map to work. They will probably go for 1 Dem sink and 3 seats for themselves if they end up gerrymandering things.

[Nyvin]

I tend to doubt that the Pubs will be willing to concede a rather safe seat for the Dems unless they have to. Does anyone disagree?

Iowa is probably not Republican enough for a 4-0 map to work. They will probably go for 1 Dem sink and 3 seats for themselves if they end up gerrymandering things.

If Polk and Dallas have to be kept together like Muon2 said then that district can't possibly get more than like Trump+2 at the very worst, and trending D at that.

[Torie]

I tend to doubt that the Pubs will be willing to concede a rather safe seat for the Dems unless they have to. Does anyone disagree?

Iowa is probably not Republican enough for a 4-0 map to work. They will probably go for 1 Dem sink and 3 seats for themselves if they end up gerrymandering things.

If Polk and Dallas have to be kept together like Muon2 said then that district can't possibly get more than like Trump+2 at the very worst, and trending D at that.

It is not clear to me that that that is a legal requirement. But the Pubs would have to reject maps to get there.

[perpetual_cynic]

I have a feeling the GOP is going to want to squeeze all the Dems into one district, but this map creates two solidly R districts, and two likely D districts.

[BoiseBoy]

Iowa official says expect first redistricting maps Sept. 16

https://apnews.com/article/health-coronavirus-pandemic-iowa-census-2020-redistricting-83575f0b849d9951463f06795004a8df