Brown CS k-means Redistricting

K-Means redistricting at Brown U

I tried this 10 years ago and it's fast and simple but it isn't good enough.

The solver in the article seems to completely ignore existing boundaries including the boundaries to which the Census has actually counted data called 'blocks' (sometimes a city block, sometimes an empty square mile of Montana). If they're assuming that population is fungible and uniformly distributed within a Census block I think that's invalid. My k-means solver drew those nice straight lines but then assigned whole blocks based on whether the center of the block was one side of the line or the other. All the districts thus had ragged edges.

Because the k-means algorithm has very few data points to fiddle (district center, district weight) it can't find complex solutions. When I ran a k-means solver it couldn't find districts with close enough to equal population in a few places.

I eventually went with a solver that considered one at a time each block on a border of two districts to see if a block would be better moved to the other district. That kind of detail and flexibility made maps that weren't as ideally simple, but still had good compactness, had much better equal-population constraint satisfaction, and should be much more workable for observing the same Census blocks that existing redistricting is done on.


Sotomayor on Gerrymandering's Absurdity

"Could you tell me what the value is to democracy from political gerrymandering?
How -- how does that help our system of government?"
"... it's okay to stack the decks so that for 10 years or an indefinite period of time one party, even though it gets a minority of votes, can't get a minor -- gets a minority of votes, can get the majority of seats?"
 -- Justice Sonia Sotomayor

from oral arguments before the Supreme Court of the United States in the case of Gill v Whitford (on the matter of gerrymandering in Wisconsin)


How the SCOTUS Wisconsin Gerrymander case could go

A. Partisan gerrymander bad! Must gerrymander districts to ensure shoddy proportional representation.
B. Partisan gerrymander bad! Map must provably have no bias.
C. Meh. Whatever. Let whatever party do whatever they want.
D. BS! Puny anti-gerrymandering arguments are so bad we don’t want any courts to listen to them in 2021 either.

I feel like the plaintiffs want A. I feel like this is pretty unlikely. It would be a truly revolutionary decision that would effectively create new rules about how every state needs to redistrict. The Court is loathe to do this. Congress could pass a new 'Voting Rights Act' type law which could do this, if Congress could pass anything useful.

Option B would be the court pulling a rabbit out of a hat. I'm not sure anyone is asking for this except me.

I would mostly bet on C. No change, no big decision either way.

I am afraid of D. The court could make a ruling such that they not only throw out the Wisconsin complaint but throw out the basis and statistical means of the Wisconsin complaint thus removing the basis for future court challenges. I know a lot of people who are betting on playing a good court challenge game in 2021 to battle the expected gerrymanders which come after the next Census. There would be a lot of searching for a new strategy between now and then if SCOTUS actively disqualifies the tests being tried in the Wisconsin case.


Things are in the news now, we can read snippets of the arguments in Court, but there won't be real news until the justices make their decision in the coming months.


Compute budget

I heard of a computational anti-gerrymandering project with a 6,000,000 cpu-hour budget on a university cluster supercomputer. I worked out that my main run in 2011 was a bit under 20,000 cpu-hours. My project at current prices with AWS spot instances or GCE interruptible instances that works out to $130-$150. That's a bit cheaper than what I paid for my home computer, and I could parallelize and do all the compute in a week instead of stringing it out over six months.


Black Votes Matter

I have perhaps spent too much time on the math and the engineering of perfect ideal non-gerrymandered districts, and it is a good ideal, and it is not enough.

The Voting Rights Act of 1965 decreed that there shall be a few majority-minority districts in states that had historically discriminated against African Americans by gerrymandering away their ability to get a majority in any congressional district. This of course introduces a different kind of deviation away from what purely 'impartial' districts might be. We might call what the VRA did 'gerrymandering for good' in that it constructed districts towards a specific end, the classic mode of gerrymandering, but for a purpose we call good. We could call it 'electoral reparations'. In an ideal world we would not need this and we would have districts that were compact or guided by enlightened social interest towards representing identifiable regions of people with common regional interest. In an ideal world ideological and identity representation would be handled by a Proportional Representation system. But we do not live in an ideal world. Voter suppression in America, whether by under equipped precincts or by gerrymandering or by the poll tax of voter-id laws, primarily hurts the poor and non-white. I hope that someday we will build a more perfect union, but for now we still need those electoral reparations.


The SCOTUS Wisconsin Case

SCOTUS will hear the Wisconsin case. They've never overturned a partisan gerrymander, only racial gerrymanders. They could also still decline to rule on this case. By 5-4 they overturned the lower court's ruling that new districts needed to be enacted for this fall, so the gerrymander persists and justice will continue to be delayed and denied.
We could argue to SCOTUS that gerrymandering is bad and it might not matter; they have to find it unconstitutional and that's a trickier thing.

The way I understand the question it's about the 'equal protection' clause of the 14th amendment and whether 'equal protection' implies 'equal representation' and that implies that people need to have representatives of their own preferred party in State Legislature and Congress. If you register D party are you only properly treated by your government if there are D representatives in proportion to the number of D voters in your state? Traditionally the answer is No, you have a representative from your district and that's what you get whether you agree with them or not. Maybe the exception for racist gerrymanders confused the issue by enacting reparations for what was clearly a pattern of minority disempowerment. I think it's a tenuous line of reasoning and certainly not an 'originalist' interpretation of the Constitution.

If they decide against Wisconsin it could be a really big deal requiring the redrawing of districts in a dozen states. I'm feeling a little cynical in betting the won't do that. If they do, it might come with a provision that nobody needs to change their districts this late and can just wait until 2021.

All that aside I of course do think that making our elected representatives more accurately mirror the voting populace is a good idea and making our legislative bodies more proportional is a good idea; I just think we'll need changes to laws and constitutions to make it happen.


Redistricting Summer School at Tufts U (Boston, MA)

Tufts University is running a special one week program on redistricting and gerrymandering this summer. There's a bunch of general interest material and three special training tracks in: how to be an expert witness in gerrymandering court battles, teaching about redistricting and gerrymandering at the high school and college level, and use of GIS software in redistricting.


Increased Interest

Emails are up. I've been getting a lot of interest in my redistricting work in the last few months. People have been writing in to ask how they might start a ballot initiative in their state. A couple state legislators have even written in to ask for details on what I've worked out for there state and if I might do some customizations for them in the future.

Sometimes people ask for an organization they can work with on practical reform efforts. In various local cases the League of Women Voters has been key, and sometimes Common Cause has been a good mover of note. The ACLU seems to focus elsewhere, but does have some redistricting work.

There's a lot of reform minded thought going around and I'm glad for it. Let's get these things nailed down by 2020 so we're ready to go when the Census data starts coming out in 2021.


Partisan Gerrymandering Supercomputing Statistical Analysis

Gerrymandering analysis at UIUC [1] uses a supercomputer cluster to generate millions of plausible districts and measures their goodness and partisan balance. Given this space of plausible district mappings, one can look at the current map and see if it is an outlier. They show one state, Maryland, and how its current map is at outlier on a couple metrics, and therefore probably an intentional partisan gerrymander. The motivation for this approach seems to be to create a tool for court challenges to gerrymandered maps. If a map is an outlier, highly unlikely by random chance, then it's probably due to malicious intent.

I wish them luck and I hope they overturn some gerrymanders. I'll probably stick to my work of making one good map to compare to. If I can make one good map that's legally and practically viable, and measure its goodness and compare to other maps, then we should just let the best map win.

[1] Election Law Journal, ELECTION LAW JOURNAL Volume 15, Number 4, 2016, DOI: 10.1089/elj.2016.0384  http://cho.pol.illinois.edu/wendy/papers/talismanic.pdf