4-District Iowa: Minimizing Population Variance

(An interesting map that would pit Latham against Braley rather than Boswell. - promoted by desmoinesdem)

County-level population numbers from the 2010 Census came out a couple days ago, and I've been trying to draw a map aimed at getting the population of each district as close to the ideal of 761,589 as possible while still retaining some degree of compactness. (Obviously, more compact districts could be drawn if one is willing to have a greater degree of variance in population.)  Here's the best I've done so far:

Proposed Iowa congressional map

I drew this map by starting each district in a corner of the state and swapping around counties until the populations were roughly even. The largest district (IA-2) is 100.03% of the smallest district (IA-1) in population.

District 1 (Blue)
Population: 761,512
2008 Presidential Vote: Obama 57.5%, McCain 41.3%
Incumbents: Braley (D), Latham (R)

The First District stretches all the way from Ames to Davenport, taking in Dubuque and Waterloo on the way. It includes both Braley and Latham's homes, which is an incumbent-vs-incumbent matchup I haven't heard much talk about.

District 2 (Green)
Population: 761,748
2008 Presidential Vote: Obama 57.7%, McCain 41.0%
Incumbent: Loebsack (D)

The Second District keeps Cedar Rapids and Iowa City together, and then sweeps south to include Burlington, Ottumwa, and most of the southernmost row of Iowa counties. It's pretty clearly an updated version of Loebsack's district, and is the most Democratic in the state.

District 3 (Purple)
Population: 761,555
2008 Presidential Vote: Obama 53.4%, McCain 45.3%
Incumbent: Boswell (D)

The Third District is based in Des Moines, but reaches north to take in Fort Dodge and includes a number of rural counties to the south. The obvious incumbent is Boswell, although the PVI of EVEN will encourage a strong Republican challenger.

District 4 (Red)
Population: 761,540
2008 Presidential Vote: Obama 47.9%, McCain 51.0%
Incumbent: King (R)

Easily the most Republican district in the state, the Fourth District includes most of northern and western Iowa, from Council Bluffs to Sioux City to Mason City. I'd expect King to hold this seat.

  • Braley/Latham would be a showdown

    It would be a real test to see if Bruce really could win statewide in my estimation or if we have been hyping the wrong person for a future campaign after Harkin's retirement.  I think he would be up to the challenge.  He has to do a better job of explaining his votes for the so called "bailouts."  I don't view them as such a thing, but the casual news observer certainly does.  

  • thanks for cross-posting

    I will bump this to the front page tomorrow.

    Your map has phenomenally small population variance. I also think Braley v Latham would be an interesting match, but I wonder if Latham would move into the new IA-03, which includes more counties he's been representing for the last decade.

    • I bet he would move into IA-03

      It seems like the smart move, especially since it includes the leaning-conservative Dallas County, which has grown quite a bit.

  • County lines?

    I can't tell from this map if you have crossed any county lines.

    • I don't think so

      not any that I can see.

    • I calculated all of the figures

      using a spreadsheet with county-level population data.  If any county lines are crossed on the map, it's an error when I used the mapping application and not an error in the districts.

  • Clarinda & Cedar Rapids

    Putting those two in the same district seems a little perverse when compared to the ghbraves maps.

    Both the blue and the green districts are starting to look gerrymandered.  That's ironic.  I always thought starting in the corners would be the sensible approach.

    Somewhere years ago I saw a formula regarding gerrymandering. It used the perimeter of the district as a data point.  These districts have pretty long perimeters compared to the earlier N, K, and G maps.  Can they be reposted so everything is on the same page?

    • these districts are clearly less compact

      as the diarist admitted--the goal here was to minimize population variance, but that doesn't have to be the sole criteria for the Legislative Services Agency.

      Silver spring's map is more compact and logical-looking while staying within the allowable population variance.

    • G = gP/A

      I found it.  see


      I suppose you guys already knew this, but some readers will not.  It's not hard to do, but I'm too lazy.  Good project for high school government classes if they can close their damn textbooks long enough to actually do some governing.

  • 40+ different plans for Iowa

    They are available at http://www.spatialdatamining.o...

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