I agree that one should aim at criteria that are close to what matters
in the lives of the people. It is more important to have districts
that people find natural than to optimize the rules from some
algorithm centric viewpoint (that is ok too, but should not take the
lead). The criteria need to be computationally feasible to check but
it is no problem whatsoever if the best identified solution is not
proven to be the best overall (as long as it is good despite of this)
(btw, the solutions at your page seemed to very good and natural from
this point of view). Generic optimization algorithms are good and
efficient enough for most purposes.
Strategies / gerrymandering is typically not a problem since the
process is too complex to master (and it is not possible to control
all the input parameters).
You discussed also the possibility of forming the districts so that
they reflect the interests of the community. One simple trick would be
to allow each atomic block to indicate which neighbouring blocks they
consider "close" vs. "distant". Those weights could be easily included
in the districting criteria. Maybe the voters could indicate their
preferences in the elections, and these preferences would be taken
into account when forming the districts for the next election. Not
necessarily a practical idea, just one example of more complex rules
that could be used if people find them useful.
You mentioned that the population of each district should be within
some given limits. That may be a good approach. One could also
determine some criterion that rewards solutions in which the districts
are of equal size. But because the size of the atomic blocks may be so
large that they would cause some distortion in the results it may be
better not to start calculating the differences (and distort the
otherwise good results) but use other criteria to determine which
solution is the best.
(One could go also further and try to use generic optimization to
count the actual election results too, and maybe also districting at
one go. That could mean e.g. different districting for each party (the
smallest party could have just one seat and one district that covers
the whole country). Nomination of candidates to different districts/
blocks could be somewhat strategic (each candidate trying to beat
other candidates of the same party).
Juho
On Nov 20, 2009, at 3:37 PM, Brian Olson wrote:
I agree with Juho. Define what a good redistricting result is,
preferably in terms that produce a single valued numeric score, and
then produce maps by whatever means you like and let the best map win.
I haven't seen a procedure defined that I was sure would always
produce good districts. While many procedures have been defined
where every step is fair, that doesn't entail that the result would
be good. There's always some side effect of the method which results
in odd unnaturally shaped districts.
My current favorite score function for district maps is*:
Minimize the average distance per person to the geographic center of
their district.
(This is currently what I've solved for at http://bolson.org/dist/ )
But this also feels tantalizingly good and might be better:
Minimize the average distance per person to the population center of
their district.
Unfortunately when laying down criteria like this, it's a more
philosophical argument rather than something that can be measured
and engineered.
I've seen lots of proposals that are purely geometric over the land
encompassed by a district, but I think that is a mistake. We're not
redistricting land. We're redistricting spatially distributed people.
*This doesn't include the _requirements_ which a map must first
pass, otherwise it is simply thrown out. 1. Contiguous districts. 2.
District populations must be within 0.5% of the average district
population.
On Nov 19, 2009, at 11:00 AM, Juho wrote:
My thinking is that it might be easier to agree about the targets
rather than the whole procedure. The targets can be simpler to
define.
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