[EM] Re STV+AV
David L Wetzell
wetzelld at gmail.com
Wed Feb 1 06:41:07 PST 2012
On Tue, Jan 31, 2012 at 11:03 PM, <
election-methods-request at lists.electorama.com> wrote:
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> dlw: In the FPTP case, it trims the ability of dissenters to move the de
>> facto center towards the true center. In the IRV case, it does the
>> opposite, it penalizes the major parties when they do not move enough
>> towards the true center.
> RBJ: again, that was not the case in Burlington. the center party was
> "squeezed" (as Jameson would say). the candidate in the center received
> nearly all of the 2nd-choice votes from voters who ranked one of either the
> left or right wing candidates 1st. it was relatively rare that the
> left-wing voter ranked the right-wing candidate as their 2nd choice and
> also vise versa. but the center candidate did not benefit from that
> because IRV is opaque to your 2nd choice if your 1st choice has not been
> eliminated. but, under Condorcet-compliant rules, the center candidate
> would have benefited greatly (and would be elected), so it can be said that
> Condorcet tends to favor the center candidate more (than either IRV or
> FPTP) whereas IRV tends to favor the largest subgroup (i.e. the Progs, in
> Burlington in 2009) of the majority group (liberals). and, we know, that
> FPTP gives the minority candidate the best chance they have of winning
> (they need a 3rd-party or 3rd independent candidate to draw votes away from
> what would be their majority opponent if the spoiler was not there).
dlw: But it is the case when you consider the incentives to vote
strategically. If in FPTP, dissenters are under pressure not to spoil, in
the IRV case, it's the supporters of the R party who are under pressure not
to spoil. IRV favors the "major party" (herein defined as one of the top
two for an area) that is closest to the true center. It thereby goads the
two major parties to move towards the center, where it is easier for
minority groups to play them off of each other to get attention to their
> dlw: Most rational choice models implicit here take as fixed the position
>> of candidates/parties on the spectrum, when in real life, this can be
>> changed somewhat. This reduces the "badness" of strategic voting. It
>> becomes less important thereby to devise an election rule that doesn't give
>> any incentive to anyone to vote strategically.
> the reason why i have never agreed with that is because people *resent*
> being saddled with the burden of voting tactically and particularly resent
> finding out ex-post facto that their sincere vote served their political
> interests more poorly than the tactical vote (the most common tactic is
> "compromising"). that resentment has consequences, one of which is a cloud
> hanging over the elected candidate as not being entirely "legitimate", not
> being the "true" choice of the electorate. but the worse consequence is
> that of holding back what would otherwise be viable independent or 3rd
> party candidates, sometimes leaving the voters with a choice between Dumb
> and Dumber. that is the *main* evil we're trying to avoid with voting
> system and ballot reform.
dlw: I think the main evil is the way the de facto center can get so
detached from the true center. If a major party refuses to adapt, it's
voters are not going to be happy. But regardless of whether they vote
strategically or not, the momentum will be for the de facto center to
approach the true center. At the end of the day, what matters is who gets
elected(how close they are to the center) and the momentum caused by the
election, not whether everyone votes sincerely and is happy with the
Single-winner elections will always tend not to elect 3rd party candidates.
That's why we need a mix of single and multi-winner elections to sustain
3rd parties that give more exit threat to minorities and check the
influence of $peech on both the major parties.
But as shown by Burlington, with IRV there can be turnover wrt who are the
major parties and that is a significant improvement.
> we are *now* experiencing some of these consequences in Burlington. the
> Progs have decided not to run a candidate (the current mayor is or was a
> Prog and is not running for re-election). it looked for a while that there
> would be only two (Dem and GOP), but recently an independent candidate
> emerged and her political appeal is a lot like a Prog candidate (the Progs
> are not ashamed of sticking up for the poor and powerless whereas, ever
> since Reagan, Democrats have modified their rhetoric to be for "the middle
> class" so as not to sound "socialistic" or too "liberal", both were bad
> words and continue to be used disparagingly in American politics). so we
> are going to have an interesting test case for the election coming up March
> 6. we might very well get an elected candidate with 41% of the vote.
> now the Progressive party in Vermont is declining *rapidly*. Burlington
> is the most populous town in the state (but Vermont has the the least
> populous largest city of all 50 states) with a population of about 42000.
> we have about 9000 voters in a mayoral election. the Democratic caucus
> had over 1000 valid voters showing up. the Prog caucus (which i attended
> as an observer, so also did another EM lister, who i just discovered has a
> Wikipedia page: http://en.wikipedia.org/wiki/**Terry_Bouricius<http://en.wikipedia.org/wiki/Terry_Bouricius>but he was a voting attendee) easily had less than 2 dozen voting members.
> 2 of the 14 Burlington city councilors are Prog. *any* of the state
> legislators have been forced to identify themselves as dual affiliated,
> Dem/Prog, in order to get elected.
> i truly fear the demise of what was once identified as the most successful
> third party in the United States.
> i'll keep you guys informed. we have an interesting real-world election
> laboratory here.
This is why we need to forge a working consensus on electoral reform to
rally around people who don't want a contested monopoly that pretends to be
a duopoly to remain in our state and nat'l politics. It seems like common
sense that we should take inspiration from our limitations and push for
electoral reforms that do not challenge duopoly but that do make it a
> ---------- Forwarded message ----------
> From: Bryan Mills <bmills at alumni.cmu.edu>
> To: David L Wetzell <wetzelld at gmail.com>
> Cc: election-methods at electorama.com
> Date: Wed, 1 Feb 2012 00:02:47 -0500
> Subject: Re: [EM] STV+AV.
>> > Why STV? The original poster wanted elected representatives to have
>> > proportional to their electoral support yes? There's no need for
>> > transfers from elected candidates then.
>> > >
>> > IRV is a form of STV, but it's not my favorite. Some of the other STV
>> > methods (e.g. Schulze-STV and CPO-STV) tend to produce better
>> > But the question of why not STV is a good one. Several reasons.
>> > STV requires much more work on the part of the voter - ranking all the
>> > down to a candidate likely to be elected, instead of just one. That
>> > probably means a much larger ballot and/or an arbitrary cutoff between
>> > ballot-candidates and write-in candidates.
>> dlw: If the number of possible rankings is the number of seats + 2 then
>> it's not too bad. And nobody would be forced to rank umpteen candidates,
>> so the low-info voters could just vote for their favorite candidate.
> The number of possible rankings is quite a lot larger than S+2. Even if
> you don't transfer votes from elected candidates, there are still C-S
> candidates eliminated -- so you'd have (C choose C-S-1)*(C-S-1)!
> distinguishable rankings, and even more if you allow equal rankings. The
> only way out seems to be to pre-filter the set of candidates, so you
> basically have to drop to approval voting at some point --
> candidate-registration petitions and the like -- and then we're back to an
> arbitrary cutoff.
dlw: You misunderstood me. If voters are only permitted to rank S+2
candidates then it's not as bad for voters.
> Partial rankings might be workable in a weighted-seat STV variant, though.
> If a vote only transfers in case of elimination (and not in case of
> surplus), one would only need to rank candidates down to the first
> candidate sufficiently likely to be elected, and you could split the ballot
> into manageable chunks by party. Determining a suitable cutoff candidate
> still has a cognitive cost, but it probably wouldn't be that bad in
If there are 3-5 seats STV then the number of candidates won't proliferate
too much and there'd be 5-7 places to vote. This would keep things
> But if we assume that partial rankings are effective, there's still the
> strategy/computation tradeoff to deal with: allowing truncated ballots
> still doesn't help with favorite-betrayal, and STV variants less
> susceptible to favorite-betrayal are also less susceptible to efficient
dlw: Truncated ballots may not end favorite betrayal, but it'll help with
> > The STV variants that are less strategy-prone are computationally
>> > inefficient, and even those are not strategy-free.
>> > And perhaps most importantly, the more resistant an STV method is to
>> > strategy, the more complicated it is to explain and understand.
>> > As deterministic methods go, I do like STV methods; but DS fixes a lot
>> > the worries I have about them.
>> dlw: One could also apply the same sort of approach to simplifying STV
>> with the
>> initial treatment of all of the rankings as approval votes to get the
>> number of candidates down to N+2, where N is the number of seats.
>> As with IRV, it's easier to explain STV when there's relatively few
>> candidates to eliminate. And, it'll mitigate the strategy effects, which
>> have to be examined more closely.
> The initial treatment of rankings as approval votes introduces some other
> problems, though.
> With an explicit "approval threshold" in the ranking, it induces a
> substantial cognitive cost on the voter (determining the approval threshold
dlw: Once again, if the no. of seats isn't that great then they'd not have
to sweat it too much. Do I rank 1, 2, 3 or 5 candidates? Who can I live
with?I'd say it's an empirical question whether such would be a reasonable
demand on voters. And I'd reckon they'd get the hang of it with some
> With an implicit "first-preference" approval, it has the same problem as
> traditional STV (i.e. IRV), namely of unduly rewarding favorite-betrayal.
> With an implicit "all-ranked" approval, the overall system would likely
> violate later-no-harm with much higher frequency; by expressing a
> preference between two dispreferred candidates one might unintentionally
> put the higher of the two in contention.
dlw: I'd say empirically we'd see just how high of a frequency LNH would be
violated. Jameson Quinn had a hard time coming up with a pathological
example for IRV3/AV3 and I imagine it'd be similar for the above. The 1st
stage would reduce the number of candidates to N+2 and it seems likely that
the N+2nd and N+3rd candidates in terms of "all-ranked" approval are less
likely to be among the N winners.
> It may well be that these issues are all less severe than in the
> deterministic alternatives to STV, but I still think they're enough to
> merit consideration of nondeterministic alternatives.
In terms of the US's political culture, nondeterministic alternatives are
not going to happen anytime in the near future and we need electoral reform
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