I meant "theoretically superior". I agree that in practice STV is a
over a century. Not to mention Fair Votes USA.
Post by Jameson Quinn
Yes, I believe that many of these references refer to what is
essentially BTV, which has been known on this list for some time
now as a superior option to STV. I'm happy that it's now in the
literature, and don't really care about naming/precedence.
It's my experience that many prop-rep voting methods can be
expressed in terms of an STV backend. PLACE, Dual Member
Proportional, many MMP variants, etc. can all be seen as just
adding options (such as overlapping seats for MMP and DMP,
biproportionality for DMP and PLACE, and partial delegation for
PLACE) on top of STV. You could therefore create new versions of
all of the above by replacing STV with BTV. I think this would be
a small step up â but not worth the additional difficulty of
explanation, in a world that's more used to STV.
2018-02-04 12:22 GMT-05:00 Kristofer Munsterhjelm
Sorry in advanced for the huge load of information all at
once, but I think you'll highly likely find the following
<https://arxiv.org/abs/1611.07105> - Two statements of
the Duggan-Schwartz theorem
<https://arxiv.org/abs/1611.07102> -Â Manipulability of
consular election rules
<https://arxiv.org/abs/1708.07580> - Achieving
Proportional Representation via Voting [ On which a blog
Better than STV and STV derivatives in all criteria? You
Post by Kristofer Munsterhjelm
From a cursory look at the latter, that looks like Bucklin
with a STV-style elect-and-reweight system. I wrote some
posts about a vote-management resistant version of Bucklin at
and found out that the simplest way of breaking a tie when
more than one candidate exceeds a Droop quota is nonmonotonic.
The simplest tiebreak is that when there are multiple
candidates with more than a quota's worth of votes (up to the
rank you're considering), you elect the one with the most
Suppose in the base scenario, A wins by tiebreak, and B has
one vote less at the rank q, so A is elected instead of B. In
a later round, say, q+1, E wins. Then suppose a few voters
who used to rank A>E decides to push E higher.
Then B wins at rank q. If now most of the B voters vote E at
rank q+1, it may happen that the deweighting done to these
voters (since they got what they wanted with B being elected
instead of A) could keep the method from electing E.
E.g. A could be a left-wing candidate, B be a right-wing
candidate, and E a center-right candidate. In the base
scenario, A wins and then the B voters get compensated by
having the center-right candidate win. But when someone
raises E, the method can't detect the left wing support and
so the right-wing candidate wins instead. Afterwards, the
right-wing has drawn weight away from E (due to E not being a
perfect centrist, but instead being center-right), and so E
Achieving monotonicity in multiwinner rules is rather hard;
it's not obvious how a method could get around the scenario
above without considering later ranks.
I'm not sure if rank-maximality solves the problem above. If
it doesn't, then the above is an example of CM failure but
not RRCM failure.
for another Bucklin PR method that seemed to be monotone.
It's also unknown whether Schulze STV is monotone, though it
seems to do much better than IRV-type STV in this respect.
And I'd add that there's yet another (very strong) type of
monotonicity not mentioned in the paper as far as I could
see. Call it "all-winners monotonicity" - raising a winner on
some ballot should not replace any of the candidates on the
elected council with anyone ranked lower on that ballot.
(There's a result by Woodall that you can't have all of
LNHelp, LNHarm, mutual majority and monotonicity. Perhaps,
due to the difficulty of stopping the monotonicity failure
scenario above, the equivalent for multiwinner would turn out
to be "you can't have either LNHelp or LNHarm, and both Droop
proportionality and monotonicity"...)
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