Redistricters, start your engines!

The 2020 Census data for redistricting is immanent starting around 2021-01-19, but we don't have official reapportionment yet! The last report from the Census bureau was "early 2021, as close to the statutory deadline as possible". If they don't have proper apportionment out by the 19th, I guess I'll start my redistricting engine based on estimates (or this estimate, or others, or some consensus I put together).


SCOTUS on North Carolina and Maryland; 2019-06-27

In a decision released Thursday, June 27, 2019, Roberts (with Kavanaugh, Gorsuch, Alito, and Thomas) wrote 32 pages amounting to, 'Gerrymandering is bad, but aw shucks there is nothing we can do'. Kagan (with Breyer, Ginsburg, and Sotomayor), rebutted in equal length 'there absolutely is something we can do and we really should have'.

One of the innovations in these court challenges was the "ensemble" method of producing thousands of plausible maps and doing statistics across likely outcomes of those maps. Kagan found that this demonstrated "the State’s map was an out-out-out-outlier" in the case of North Carolina's map which was worse than all 3000 other proposed maps it was compared to. Roberts mocked this claiming, "Judges not only have to pick the winner—they have to beat the point spread." Roberts at other points wanted to avoid such 'hypotheticals', but Kagan found that "... the same technologies and data that today facilitate extreme partisan gerrymanders also enable courts to discover them, ..." Kagan isn't afraid of technology, it's not some weird magic black box to her. It's a tool, and it's not some weird hypothetical, it's a tool actually used to create real and effective gerrymanders, and the same tools can analyze and pick apart those gerrymanders.

With great handwringing, Roberts repeatedly claimed that there was no solid rule on which to base a decision or decree a change. Kagan responds with a long list of citations of Supreme Court and other Federal Court decisions that found rules and made decrees.

Roberts implicitly suggested that Congress and State Legislatures could make laws creating such rules. He cited a list of bills relating to redistricting rules to which Kagan responded, "what all these bills have in common is that they are not laws. The politicians who benefit from partisan gerrymandering are unlikely to change partisan gerrymandering. And because those politicians maintain themselves in office through partisan gerrymandering, the chances for legislative reform are slight." (Emphasis Kagan's)

Kagan doesn't think we should wait for ballot initiatives either: "Fewer than half the States offer voters an opportunity to put initiatives to direct vote; in all the rest (including North Carolina and Maryland), voters are dependent on legislators to make electoral changes (which for all the reasons already given, they are unlikely to do)."

And on independent commissions, "Some Members of the majority, of course, once thought such initiatives unconstitutional. See Arizona State Legislature, 576 U. S., at ___ (ROBERTS, C. J., dissenting)"


Looking Forward

Should we have Congress make a law restricting gerrymandering nationwide? Absolutely. We should have a new Voting Rights Act that ensures a fair process in every state. We should also have a Congress that will pass it and a President who will sign it.

We should also have a Court that will do their job. For over two hundred years the Supreme Court has been a check against bad laws. Gerrymandered district maps passed by state legislatures are bad laws. Instead of using their encyclopedic knowledge to write 32 pages of "we don't wanna" they should have done their duty to the Constitution and the people of the United States of America and defended our democracy.


"ALURE" Blocky Recursive Districts

Another algorithmic redistricting implementation! "ALURE" (ALgorithmic Universal Redistricting Engine) (their only web presence seems to be that facebook page) looks like another recursive split algorithm like "shortest splitline", but keeping to north-south and east-west cuts and boxes.

It makes districts. They're pretty simple. Given the alternative of complex gerrymandered monsters simple sounds like a good feature.

My usual criticisms of "process" oriented districting applies. Nothing about this process will necessarily produce "good" districts. Its simplicity ignores all existing county and city boundaries which would make it hard to manage. (Something my own software misses too, which I 'm working on for 2020.)


Chris Larson method of automatic redistricting

A new automated redistricting algorithm has appeared with concrete examples for Michigan and Virginia. It sounds like it's doing something like a minimum cut through the blocks that have lowest population. It winds up doing this in mostly horizontal or vertical lines, based on how the Michigan map looks. It mostly keeps counties together, but when it decides it needs to cut it can make a long cut on a straight-ish line through many counties.

In the dichotomy of solutions being "fair process" vs "good outcome" this is another "fair process" entry. I like its output subjectively better than the "shortest splitline" algorithm, and the county-cohesion feature will make it more practical, but I still think there's nothing inherent in its structure that will ensure a "good outcome". I still prefer to start at the end, define what kind of outcome we want, and achieve that by whatever methods happen to work. If we have the right metric, then optimizing to it will be okay. (On the other hand, the last century of industrial best practices point out that picking the right metric is problematic and good process needs to be blended with metrics for actual best outcomes.)



Clean Missouri Shoddy Proportionality

Missouri passed the "Clean Missouri" "Amendment 1" last November, and among other things it changes how redistricting gets done there.
tl;dr: they did some weird things I think will have messy unintended consequences

In 2021 they'll appoint a "non-partisan state demographer" who will do the first pass at map drawing. But the law has a pretty strict set of rules to design to.
In order of priority:

  1. Equal Population
  2. No racial bias (or could be read to require VRA style gerrymandering-for-good)
  3. "Partisan fairness and, secondarily, competitiveness". Fairness being: "the difference between the two parties’ total wasted votes, divided by the total votes cast for the two parties, is as close to zero as practicable." Furthermore, competitiveness: "simulate elections in which the hypothetical statewide vote shifts by one percent, two percent, three percent, four percent, and five percent in favor of each party. The vote in each individual district shall be assumed to shift by the same amount as the statewide vote. The non-partisan state demographer shall ensure that, in each of these simulated elections, the difference between the two parties’ total wasted votes, divided by the total votes cast for the two parties, is as close to zero as practicable"
  4. Contiguous
  5. Respect existing political boundaries
  6. Compactness

Political Fairness and Competitiveness

Their "Political Fairness" is what I call proportionality. It's interesting that they come at it from wasted vote, and I think that's probably a good measure, it's just a little inside out and backwards of how I usually frame this. I'd usually say "the party with 60% of the people should get 60% of the seats in the state legislature", but they're saying "the party with 40% of the people shouldn't have proportionally more of their votes wasted in districts they don't win than the other party wastes in districts it doesn't win". This 'efficiency gap' was a big deal in a recent case in Wisconsin that got to the Supreme Court (but SCOTUS declined to accept the efficiency gap as a sufficient measure for determining a gerrymander they'd overrule). It remains to be seen if the efficiency gap is really a good measure or a statistical fad.
Their measure of "Competitiveness" also comes directly out of recent research into gerrymandering. People have done similar analysis in Wisconsin and Michigan and determined that they disadvantaged party is not only not getting proportional representation but they would have to win huge shifts in the electorate and huge landslides in order to catch up. I'm not sure this specific proscribed simulation is actually a good statistical method though. The law goes as far as describing the statistical model, saying that each district shall be simulated to shift by a specific formula, and I kinda expect we don't yet have the best model for doing those simulations.

Trying To Predict Unintended Consequences

If we're lucky, in the best case, this system will result in a Missouri State Legislature that on average reflects the citizens of that state.

That "on average" is a hedge because I think they'll get a lot of messy districts. By messy I mean non-local, tentacled monsters; the hallmark of gerrymandering. But maybe that doesn't matter? One thing I keep running into around US culture and representative government is that people identify with their place less and less. So, I hear some voices of dissent saying that it's weird to be in a district with some random people over there connected by a squiggly district, but also I hear people not caring about that and just caring about whether they can vote for and elect someone who agrees with their values. If more people can get that, being represented by someone they kinda like, maybe that's a good thing. If the State Legislature more accurately reflects the average of the people in the state, that's a good thing, messy though this way might be.

But it could also lead to 10 years of unmitigated incumbency. Before California moved to an independent redistricting commission, they had a bipartisan gerrymander where everyone had a safe seat and incumbency was rampant. This system could easily produce that. Or it might produce half safe seats and half "competitive" seats designed to be closer to 50/50 between the two major parties. If you're living in a safe seat district, you're stuck with that and your vote (except maybe at the primary) will never really matter.

I'm curious if they'll actually break contiguity or if that will sneak back up to its traditional place next to equal population.

Lastly, with compactness at the bottom of that heap, we can pretty much ignore it.

What About Future Laws?

I also think it's just kinda fascinating that this oddly specific law passed. Missouri Republicans are contemplating a try to repeal it, but if they don't it should be a fascinating experiment in democracy. I guess we'll know how it goes some time around 2022 or 2024. I wouldn't recommend following this law as a model, but hey, let's see how it goes?


What is "Proportional"? Apportionment Algorithms

I think by “Proportional” we mean a linear interpolation, the number of seats allocated to various populations should scale linearly with those populations.

I was writing this up in code and ran into some subtleties and wanted to share.

First, the US House apportionment algorithm is not proportional! It allocates one seat to every state and then approaches linear after that. Wyoming never quite comes back in line.

Second, integer linear interpolation on many dimensions simultaneously can be subtle. I modified Bresenham’s integer linear interpolation algorithm (common in computer graphics) but tried two different ways of applying it in parallel to many lines at once and made a minor bug on my first try, so I want to share what I learned. My first attempt was to cycle through all the groups in descending population order to see if they needed a next apportionment seat; and just repeat this until all the seats were apportioned out. My better algorithm does a pass through all the groups, then re-sorts them based on how far behind the line they are and how much they need a next seat. Repeating these two steps works better: passing through all the groups - maybe allocating, then re-sorting all the groups based on updates.

The second line below is populations for 4 hypothetical groups or states. For 9 seats there would be 0.009 people per seat if everything were fair.

target p/s      0.009
pops              15         44        368        573
house              1          1          3          4
house p/s  0.0666667  0.0227273 0.00815217  0.0069808
nb 1               0          1          3          5
nb 1  p/s          0  0.0227273 0.00815217   0.008726
nb 2               0          0          3          6
nb 2  p/s          0          0 0.00815217  0.0104712

Above you can see the House algorithm, my algorithm versions 1 and 2. Each pair of lines shows the seat allocations and the “p/s” population/seat. The House algorithm has some large over-representations of tiny groups and resulting under-representation of other groups. My final algorithm avoids this.

The House algorithm is probably still the right answer for the US House. More broadly I want to figure out a good definition of what is fair for Proportional Representation. In PR one could simply say that a group that is 33% of the population should get 33% of the seats, but if there are 10 seats should they get 3 or 4? That depends on the various sizes of other groups being represented. I want to codify this into good rules for what is fair and ideal, and then do work on practical systems that can as closely as possible achieve this.

My apportionment code in Python on github


Gil v Whitford decision; 2018-06-18

The Supreme Court of the United States (SCOTUS) gave a 41 page document around political gerrymandering in Wisconsin. Below are my notes.

The main decision was a unanimous procedural action to bump the case back down to District Court. A concurring opinion from Kagan, Ginsburg, Breyer, and Sotomayor laid out a road may for the plantiffs to fix their case and come back and try again. I believe there is one more legal challenge not sufficiently pursued in this case.

The Procedural Rebuff

Chief Justice Roberts, et. al., primarily ruled that the plaintiffs had not sufficiently shown 'standing' for their case. They had to show that they had personally been harmed by the effects of gerrymandering. The plaintiff most cited, who must have done most of the talking during the original case, wasn't from a badly gerrymandered district. Even measuring gerrymandering is problematic and they don't like most of the measures.

The Court is aware of the mediocrity they have contributed to this situation. "Our previous attempts at an answer have left few clear landmarks for addressing the question." (p.8)

What they most wind up looking at is 'dilution of votes'. But, "To the extent the plaintiffs’ alleged harm is the dilution of their votes, that injury is district specific." (p.14) SCOTUS seems to want district by district, 'this one was packed', 'this one was cracked'. They disparage systemic, state-wide statistics, but want to focus on effects on concrete single voters.

The main decision claims that the fix could be small:
"Remedying the individual voter’s harm, therefore, does not necessarily require restructuring all of the State’s legislative districts. It requires revising only such districts as are necessary to reshape the voter’s district—so that the voter may be unpacked or uncracked, as the case may be." (p.16)
The concurring decision later suggests getting plaintiffs from every packed or cracked district, so that the result will wind up affecting pretty much all the districts.

On the "Efficiency Gap" measure:
"The difficulty for standing purposes is that these calculations are an average measure. They do not address the effect that a gerrymander has on the votes of particular citizens. Partisan-asymmetry metrics such as the efficiency gap measure something else entirely: the effect that a gerrymander has on the fortunes of political parties." (p.20)

7 of 9 members of the court felt that the case still had a chance though, so they bounced it back down to District Court. Thomas and Gorsuch wanted to just close the case and let the gerrymander stand.

The Concurring Hope

The Kagan, Ginsburg, Breyer, Sotomayor concurring opinion mostly calls out ways to make the anti-gerrymandering case better. They suggest that there's a good First Amendment claim to be made around freedom of association and the ability to effectively coordinate as a political party.
"... a plaintiff presenting such a theory would not need to show that her particular voting district was packed or cracked for standing purposes because that fact would bear no connection to her substantive claim."
"... everything about the litigation of that claim—from standing on down to remedy—would be statewide in nature." (p.2)
The main decision had a few notes, as SCOTUS frequently does, of "not our job" because they want lawmaking to be done by the legislatures and the congress, but this critique notes that,
"... only the courts can do anything to remedy the problem, because gerrymanders benefit those who control the political branches." (p.2)

They cite "Wesberry v. Sanders, 376 U. S. 1, 7 (1964)" for the "one-person, one-vote" principle and how fractionally diluting a vote is bad.

This to me sounds like an endorsement of the rising "ensemble" method of statistically challenging gerrymanders:
"In many partisan gerrymandering cases, that threshold showing will not be hard to make. Among other ways of proving packing or cracking, a plaintiff could produce an alternative map (or set of alternative maps)—comparably consistent with traditional districting principles—under which her vote would carry more weight." (p.3)

How to get a state wide effect for the state wide problem, more plaintiffs from all the packed and cracked districts:
"Assuming that is true, the plaintiffs should have a mass of packing and cracking proof, which they can now also present in district-by-district form to support their standing. In other words, a plaintiff residing in each affected district can show, through an alternative map or other evidence, that packing or cracking indeed occurred there." (p.6)
"... with enough plaintiffs joined together—attacking all the packed and cracked districts in a statewide gerrymander—those obligatory revisions could amount to a wholesale restructuring of the State’s districting plan." (p.7)

The main opinion claimed that the intent of the legislature didn't matter (documents were presented about deliberate gerrymandering) only the resulting injury to specific voters. Kagan, et.al., cite "Alabama Legislative Black Caucus v. Alabama" claiming that motive evidence counts and that statewide systemic evidence counts.

Getting back to the First Amendment free-association claim:
"The complaint in such a case is instead that the gerrymander has burdened the ability of like-minded people across the State to affiliate in a political party and carry out that organization’s activities and objects." (p.10)
"... nothing in the Court’s opinion prevents the plaintiffs on remand from pursuing an associational claim, or from satisfying the different standing requirement that theory would entail." (p.11)
The opinion closes with notes about how gerrymandering is bad and it hurts America and it has gotten a lot worse in the last two decades.

One More Thing

From the main opinion:
"The 99 members of the Assembly are chosen from single districts that must “consist of contiguous territory and be in as compact form as practicable.” §4. " (p.2)
What if the whole case is really much simpler? I can trivially show that the Wisconsin districts are not as compact as practicableThe Legislature of Wisconsin broke Wisconsin's laws. Just as in the recent Pennsylvania case, that's all you need. State court can throw out the gerrymandering.