What’s a district for?

I talk about redistricting with a lot of people. I hear a variety of goals for what people want to achieve with redistricting. We know it is possible to arrive at partisan and racial gerrymandering with redistricting. What else might we want out of redistricting?

• Competitive elections: as many districts as possible should be close to 50%/50% split between The Two Parties.
• Proportional representation: Overall, across a state or nationally, the legislative body elected should reflect the party, ideology, race, or ethnicity of the populace. For example, a population that is 20% green Martians should elect a legislature with 20% of the representatives being green Martians.
• Compactness: districts should be geometrically nice, like soap bubbles.
• Follow existing boundaries: Counties and cities should be divided as little as possible.
• Regional identity: If a group of people in an area identify as a region, this should be observed.
• Fair Algorithm: Design a process to follow that can’t be subverted.

I think it’s obvious we can’t get all of those things at the same time. I think I hear the most desire for competitive elections and proportional representation the most, and I think districts aren’t the right solution for those things.

Ohio just amended its constitution to change how state legislature districts are drawn ( http://blog.bdistricting.com/2015/12/ohio-bipartisan-redistricting.html ). Compared to the US Constitution, state constitutions are being amended all the time. I want to see a state change the whole way its smaller legislative body is elected to be an at-large, non-districted proportional representation system using Single Transferrable Vote (or another proportional representation election method). Single Transferrable Vote and related methods take in votes where people rank the candidates (1st, 2nd, 3rd, etc.). In short, try to give everyone their first-choice representative. If your first-choice candidate didn’t get enough support to qualify for a seat, maybe your second choice will. If your first choice was wildly popular, you’re part of a large faction and you might get both your first and second choice. If electing 20 seats, any group that can get together 1/20th of the vote should be able to get someone elected. A major party might run a slate of candidates and get 8 out of 20.

That’s great, but what’s a district for? A district is inherently geographical. It isn’t ideological. It isn’t racial. It can be those things if you make it that way, but a district is just a line on the map (with some people inside). To me, a district should balance the three factors of regional identity, following existing boundaries, and compactness. I don’t think there’s a hard priority to those three issues. Existing boundaries make a district easier to administer. Regional identity is important. Either of these might not divide conveniently into the right size chunks. If you can’t get those two things, draw the line compactly, if for no other reason than that it’s the opposite of the far-reaching, gerrymandering tendrils of some mapping horrors out there.

The US as 50 equal population states

The US as 50 equal-population states.
This looks like it was a hand-tuned project, and as such has one person's understandings of what regions go together naturally. In some ways, this is better than an automated solution; it may be missing the mark in some places, but overall, I think it looks really good.

Ohio Bipartisan Redistricting Commission Amendment

Ohio Bipartisan Redistricting Commission Amendment


This actually passed by popular referendum in November 2015. It's an interesting bill with a few wrinkles I haven't seen in other "independent commission" model plans. It has a lot more rules that bind that commission to produce a specific map. I guess we'll really know how it goes by September 2021, when the first result of this process is due.

Paragraph 3.B.1 allows for 95% to 105% of the ideal population of a district. This is an important legal precedent (unless it is maybe someday overturned by SCOTUS deciding that a stricter rule would be needed to satisfy "one person, one vote"). My maps hold to plus or minus 0.5% in almost all cases.

Sections 3.C-E define an algorithm! It might be unsatisfiable, but it has an escape clause. If a county happens to have 95% to 105% of the ideal population, it must be kept whole as one district. More populous counties are supposed to contain whole districts and one leftover region that merges with a neighboring district. It ends with, “Where feasible, no county shall be split more than once,” which I expect to be unenforceable.

3.D.2 “Representative districts shall be drawn so as to split the smallest possible number of municipal corporations and townships…” This is an interesting measure. I could automatically count this in my programs.

3.D.3 “… not more than one municipal corporation or township may be split per representative district.” This is another fascinating requirement, and I also expect it will be necessary to break it. But, it is easy to count.




And then there are a bunch of tedious tiebreaker-type rules for when the rules have to be broken.

Section 6.B calls for Fake Proportional Representation! “The statewide proportion of districts whose voters, based on statewide state and federal partisan general election results during the last ten years, favor each political party shall correspond closely to the statewide preferences of the voters of Ohio.”


I could probably write a program to do this whole process automatically. Lower down on Ohio's list of requirements is to "make compact districts." My code can do that quite well. Taking all of these requirements together, there's approximately zero wiggle room for the commission to actually do anything. We may as well save ourselves some money and automate them out of a job. Hire me for six months or a year, and I'll write the program to do it. It'd be a bargain.

10 years of algorithmic redistricting

Found an entry in my diary. Algorithmic redistricting with a home computer became possible in about 2005 when I was using a PowerMac G4 with 1.25 GB of RAM.

Redistricting Reform Act of 2015

On 2015-04-30, four House Democrats announced the "Redistricting Reform Act of 2015" ( bill text ).

tl;dr: It's pretty good. Everyone should call their congress member and ask them to support the Lofgren/Brownley/Lowenthal/Edwards "Redistricting Reform Act".

From the press release:

Under the Redistricting Reform Act of 2015:

• Each state would be required to establish an independent, multi-party redistricting commission to draw Congressional district maps.
• Specific eligibility requirements ensure that members of the commissions cannot have certain conflicts of interests, such as lobbyists, political donors or party operatives, and must reflect the diversity of the state while operating transparently.
• The criteria for a redistricting plan developed by the independent commission provides that districts must:
• have equal population per representative, in accordance with the U.S. Constitution;
• comply with the Voting Rights Act of 1965;
• be geographically contiguous and compact, as well as have boundaries that minimize the division of any community of interest, municipality, county, or neighborhood. (see below, this summary isn't quite right -B)
• The commission must provide ample notice and opportunity for the public to provide input and engage in the redistricting process.

A lot of the bill text is about forming the commission. Like many states that are trying this sort of 'independent commission' model it's a big unaccountable lottery where nobody knows what we'll get. The good news is that it has a better structure. Some states make a commission that's half D and half R (with a system of nomination and veto where the Legislature controls the pool of people from which the commission is eventually randomly chosen). This plan calls for 12 people, 4 from the largest party, 4 from the second largest party, and 4 from other parties or no party. I like this better than simply enshrining the Two Party System into a commission that's half one and half the other.

A quibble about that summary: the bill text prioritizes not splitting 'a community of interest' over compactness. The priorities are: 1. equal population, 2. Voting Rights Act, 3. contiguous, 4. community of interest, 5. compact. "Equal population" is supposed to be "as nearly as practicable", which will probably be grounds for a court action sooner or later. Some states take this as one voter, some states vary by a few hundred (out of about 650,000).

I think that might even be a good priority of things to optimize for. Probably the VRA will never push a district mapping to be non-contiguous, so that order shouldn't matter much. For me the biggest question is how to weight 'community of interest' vs 'compact'. That will be a real and actual balancing game that probably will make somebody unhappy somewhere.

The other good news about this bill is that it says a lot about transparency of process and the kind of meetings and public meetings and web presence the whole process should have. And, it sets a reasonable deadline of August 15, 2021 (following the 2020 Census) for these plans to be delivered. Plenty of time before the 2022 congressional elections. In the current cycle, there are some states that have just had their redistricting invalidated in court in 2015 after the 2010 Census, and that's ridiculous.

Lessons Learned

1. Computers can solve redistricting, impartially, unassisted, with precision probably good enough to pass a court challenge. A home computer left to itself for a week can do everything your state needs.
2. Those maps (so far) have some shortcomings and inconveniences in realpolitik. Sometimes the lines are annoyingly just a little bit off of city/county lines where actually following those lines would be just as good and make everything easier to administer.

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Originally I thought that maybe we could enact just purely the automatic maps. Now I think that wouldn't quite work well.
One solution might be that the legislature gets to draw a map that cannot deviate by more than 5% from the ideal impartial compact map. Even better if they have to publish some sort of audit log about why they make each change. Shenanigans would be limited and detectable.
A persistent core philosophy might be: define a measure for what a good district is
Define a philosophy of what we want out of district mappings, then design a mathematical measurement of that.
(But be careful when designing metrics because the devil is in the unexpected emergent properties of optimizing towards those metrics.)

Lastly, automatic "gerrymandering for good" as mandated by the Voting Rights Act would be hard, but maybe we don't have to anymore after a SCOTUS decision last year.