[EM] CMU's "cake cutting" solution to gerrymandering

Kristofer Munsterhjelm km_elmet at t-online.de
Thu Nov 9 06:29:46 PST 2017

On 11/09/2017 12:33 AM, robert bristow-johnson wrote:
>> On 11/08/2017 06:05 PM, Rob Lanphier wrote:
> <https://www.axios.com/researchers-propose-a-gaming-solution-to-gerrymandering-2507567048.html>
> i read through this article and got the gist of it.
>>> I haven't done the deep dive on this yet, and have some gut instinct
>>> reactions, but I'm curious: what do you all think? Assuming dividing
>>> states into voting districts is a necessary evil, is this as good a
>>> way as any to do it?
>> I suppose it might lead to "bipartisan gerrymanders", where the parties
>> reach an agreement about how which incumbents should survive until the
>> next election, rather than the voters being the ones to choose. In
>> effect, you would get something between closed party list and SNTV, with
>> two parties.
>> Furthermore, the proposal doesn't specify who gets to participate in the
>> cake-cutting process. If it's t1/he parties who are currently in power,
>> rather than the cake-cutting process being done just after the election
>> (before seats are given out), then incumbent parties could cooperate to
>> block a growing challenger party by cracking the challenger party's
>> support across multiple districts. Thus it could strengthen Duverger's
> law.
>> I would prefer the independent commission solution if the commissions
>> can be trusted to be independent. If they can't be, then closed party
>> list with a (variable, implicit) threshold could be preferrable to the
>> kind of one-sided gerrymander that exists now.
> and i think that algorithms that make a meaningful measure of
> compactness or convexity of the districts is important to use.  and i
> think they could weight this convexity measure along with other
> properties that maybe can have objective measurement.  like how well
> "communities" (however they are defined) are kept intact.  so when
> district boundaries for some legislative district align well with
> existing city or town or county boundaries, that gets you points of some
> weight also.  but also given demographic maps of cultural populations.
> of course a salient measure is the variance of the district population
> (or a 1/C scaling of the population if the district has C candidates at
> large).
> another salient metric is, of course, given known precinct vote counts,
> how proportional legislative body is to the voting population.  i have
> an idea how to define that metric.
> there could be different weighting factors but you could literally have
> a "goodness" vector that would evaluate all of these different metrics
> and represent that as a dimension of the vector.
> then commissions could transparently display all of the different maps
> they cooked up and what that vector might look like for different sets
> of weighting factors.  it's still a political and "qualitative" decision
> by a commission, but it would bit quantitatively restricted. (e.g. the
> Supreme Court allows for a 10% max variation of population per elected
> seat in the district, but does not require each district to have the
> same number of elected seats. my state senate district is known to be
> the legislative district in the U.S. with the most number of elected
> seats, which is 6.)
> This redistricting and gerrymandering problem really needs to be
> solved.  this is actually a more salient problem than the dearth of
> ranked-choice voting in the U.S.

 From over here, I'd say the best way to solve the problem is to 
dissolve the problem, as it were; to make the thing that leads to the 
problem in the first place, go away.

In other words, replace single winner districts with multimember ones, 
or add top-up seats like in MMP.

I guess the second order problem is that such solutions may be 
unpalatable due to US political history. In addition, where they have 
been tried (e.g. New York STV), they've solved the problem too well, 
drawing ire of those who benefitted from the old way of doing things.

Even if the redrawing can be made impartial, there's a difficulty with 
single member districts in that you can't ensure that the natural 
boundaries (different communities, landmarks, etc) line up with the kind 
of boundaries you'd need to get political proportionality or fairness.

(You could probably redraw districts just after the election, before any 
seats are apportioned, in such a way that you'd get political 
proportionality, but then the method would in effect be a multiwinner 
one - it'd  just look like a bunch of single-winner ones after each 

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