[EM] More on Gerrymander prevention

Michael Rouse mrouse at cdsnet.net
Thu Mar 28 22:22:11 PST 2002

Well, Oregon (the state I live in) has the requirement that districts be
contiguous and connected by transportation links. Drawing districts based on
the efficiency of such transportation links is step beyond that, but a
logical one. It would certainly be worth looking at.

I am kind of leery, though, about a method that would encourage
representatives to build interstate highways in odd locations, or (worse)
and incentive to block needed roads. "That road is far too Republican for my
district" or "This freeway needs a loop two miles west, then four miles
north, then west again." Of course, this argument has nothing to do do with
my preference for vote-based centroidal Voronoi polygons for districting....

Michael Rouse
mrouse at cdsnet.net

----- Original Message -----
From: "Anthony Simmons" <bbadonov at yahoo.com>
To: <election-methods-list at eskimo.com>
Sent: Thursday, March 28, 2002 8:31 PM
Subject: RE: [EM] More on Gerrymander prevention

> Josh's proposal is indeed a very slick idea.  It groups
> people according to social and economic criteria.  It would
> work out well where I live -- on the west side of Puget
> Sound. Seattle is not far away, in miles (kilometers,
> lightseconds ...), but it may as well be another planet.
> And the conductivity analogy is a good one, but it might have
> to be modified a bit.  Certainly, conductivity of two
> parallel roads is the sum of their conductivities, but two
> roads in series shouldn't have any less conductivity (more
> resistance) than the least conductive point in the circuit.
> Or perhaps slightly less on average, since there's a greater
> chance of a bottleneck from an accident.  So the rules would
> be more like:
>     C1, C2, C3, ..., Cn in parallel:  C = sum of C1, etc.
>     C1, C2, C3, ..., Cn in series:    C = Smallest of C1, etc.
> One thing I would try to add would be a measure to even out
> the distribution of power (as measured by Banzhaf or
> whatever).  It's step two, below.
> As an alternative to maximizing conductivity of the entire
> graph (if I might adopt the electrical metaphor, which I
> think is inspired), how about this for breaking up the
> country into districts of N people each:
>     1.  Find the single collection of N people that has the
>         smallest total conductivity.
>     2.  Slide the boundaries in order to make the political
>         makeup (as determined, perhaps, by party
>         registration) as close as possible to the average in
>         some larger area containing the district.  Do this by
>         moving boundary sections with the greatest gradient -
>         - that is, move the parts of the boundary that have
>         the greatest effect on political makeup per unit area
>         change.  Some parts get pushed out to enlarge the
>         district; others get pulled in to reduce it by the
>         same amount.  The idea is to slide the district in a
>         fashion that gets it as close to the average makeup
>         for the region with the least possible adjustment.
>         The reason for this step is to eliminate, as much as
>         possible, differences in individual power because of
>         differing power indices for voters in different
>         districts.
>         I'm not sure if deliberately rendering the districts
>         more typical of the surrounding political environment
>         is the right correction.  It depends on what measure
>         we choose in order to measure gerrymandering; the
>         idea is to jiggle the borders to reduce that measure.
>         I think this would be more reliable than just
>         assuming that gerrymandering is minimized by
>         selecting the right procedure.
>     2.  Record the district thus created, and remove those
>         people from the map.
>     3.  If there are still people left, go to (1).

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