[EM] IRV etc. v. EPR-STEVE'S REPLY TO KRISTOFER
km_elmet at t-online.de
Fri Jul 20 02:30:20 PDT 2018
On 2018-07-18 11:41, steve bosworth wrote:
> Hi Kristofer,
> Thank you for originally telling me about MJ and helping me think that
> it might be possible to modify it to enable evaluative voting also to
> elect multi-winners.Do you see any flaws in EPR?Below, you helpfully
> illustrate how some varieties of voting by ranking candidates might
> produce somewhat similar results.However, do you agree with me that,
> unlike any of these varieties, EPR alone allows each voter to guarantee
> that her one vote will be added to the one representative whom she has
> helped to elect and sees as the one most ‘fit’ for the office?
Since you have added maximum weight limits to the EPR method, it seems
that either it is not completely free of vote-wasting, or an unweighted
method can be made free of vote-wasting as well.
Just set the maximum weight limit to (number of voters)/(number of
seats), and you will get an Asset-based method very close to BTV
(Bucklin STV) with a Hare quota. If a group of voters' favorite
candidate gets more than a Droop quota, that candidate will then decide
where the surplus goes. This is similar to, but not quite the same
thing, as the surplus redistribution step in ordinary BTV.
If this Asset BTV method (to coin a name) wastes votes, then EPR can be
slowly changed into this Asset BTV method, there must be some value of
the maximum weight restriction that turns EPR into a method that wastes
votes. Alternatively, EPR continuously approaches a vote-wasting method
as one decreases the maximum weight restriction. But in that case, since
EPR as you propose it already has a maximum weight restriction, it can't
be the minimally vote-wasting method: that method would be EPR without
any maximum weight restrictions at all.
In short: by being more strict about the maximum weight winners can get,
we can get an unweighted method. You've said unweighted methods waste
votes. It's possible to turn EPR into an unweighted method by decreasing
the max weight restriction. So somewhere along that line from no
restriction to a Hare quota restriction, EPR turns into a vote-wasting
method. But what this point is, is entirely arbitrary. Hence something
strange is going on.
Another way to pry at this is to consider normal Asset. Suppose we
instead of EPR use a method where everybody who gets one or more votes
meet up and redistribute their votes, Asset style, until only (number of
seats) of the candidates have more than zero votes. (For the sake of
simplicity, ignore the problem of scale at the moment.) Since EPR has an
Asset component yet doesn't waste votes, why would this Asset method
waste votes? If it wastes votes, something strange is going on; if it
doesn't, then EPR is not the only method that doesn't waste votes.
From a cursory look, Asset doesn't appear to waste votes quantitatively
because a voter X's vote either helps his favorite Y, or helps someone
who Y contributes asset to (who then becomes the candidate X helped
elect). It doesn't waste votes qualitatively any more than EPR does
because X's vote contributes directly to the initial assets of Y.
I suspect that the answer is that every method wastes votes somewhat,
and some are better than others. But I also imagine that it's hard to
quantify either to what degree a method wastes votes, or to what degree
it is a bad thing. This because while the grades in MJ are compared to a
common standard, that common standard might differ in different societies.
As I've understood it, a wasted vote in something like Bucklin STV
implies that either the voter's ballot has been exhausted (e.g. he only
named a favorite, nobody else, and now his vote won't count for anything
any longer), or that the method forced his vote to count towards a
compromise rather than to his favorite. Sometimes, a compromise is a
choice everybody can accept; other times, it's a choice that pleases
nobody. And those two situations differ.
If it's only properly exhausted ballots that cause trouble, the
minimally vote-wasting unweighted method could just have the otherwise
truncated ballot be completed according to the favorite's choice: the
grades not supplied by the voter would then be supplied by the default
ballot provided by the voter's favorite candidate.
On a side note, I think that redoing the method with a different initial
threshold is better than changing the initial threshold during the
process, as everybody gets to play according to the same rules. It is
also more complex, however.
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