<div dir="ltr"><div dir="auto">I think we may need a better theory to explain why IRV elects the Condorcet candidate with near-perfect frequency in practice. We're now somewhere around 215 IRV elections in the US since San Francisco started in 2004, and Burlington 2009 is still the only case. That includes many highly competitive, crowded fields with more than 2 strong candidates, including the Minneapolis mayoral race last year and the San Francisco Mayoral race and Maine Democratic gubernatorial primary this year. Probably a decent research project there for the taking.</div></div><br><div class="gmail_quote"><div dir="ltr">On Thu, Dec 20, 2018, 2:33 PM Richard Lung <<a href="mailto:voting@ukscientists.com" target="_blank">voting@ukscientists.com</a> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<div class="gmail-m_-4726504696247793351m_7433369598014388013moz-cite-prefix"><br>
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<div class="gmail-m_-4726504696247793351m_7433369598014388013moz-cite-prefix">Following is repetitive but not
everyone will have heard it. The classic judgment is by Simon
Laplace (backed by JFS Ross), who decided in favor of Borda method
over Condorcet method, because ranks are not of equal importance.
Condorcet has since been weighted (and not arbitrarily like
Borda). But Condorcet appears to be generally a cross-referencing
of some given voting method, for internal consistency, not a
method in itself.</div>
<div class="gmail-m_-4726504696247793351m_7433369598014388013moz-cite-prefix">IRV/RCV/Alternative Vote suffers from
premature exclusion of candidates. Perhaps because USA is
two-party polarised, the Burlington result has not repeated yet. <br>
</div>
<div class="gmail-m_-4726504696247793351m_7433369598014388013moz-cite-prefix">An IRV drawback is also potentially
true of STV, especially in small multi-member constituencies. In
Ireland in 2016, two brothers got supporters to allocate extra
first preferences to younger brother, to ensure not excluded on
first elimination count. They were elected the two most popular.</div>
<div class="gmail-m_-4726504696247793351m_7433369598014388013moz-cite-prefix"><br>
</div>
<div class="gmail-m_-4726504696247793351m_7433369598014388013moz-cite-prefix">My invention does not eliminate
candidates, tho it uses exclusion counts, as well as election
counts: "FAB STV: Four Averages Binomial Single Transferable Vote"
maximises ranked choice information by counting all ranked
choices, thru keep values (weighting) of preference and
unpreference (reverse preference) and, in both cases, abstention
(possibly making a quota for leaving a seat empty). <br>
</div>
<div class="gmail-m_-4726504696247793351m_7433369598014388013moz-cite-prefix">Official elections are generally
"uninomial" (preference-only)</div>
<div class="gmail-m_-4726504696247793351m_7433369598014388013moz-cite-prefix">The difference of FAB STV from the
voters viewpoint is that they have Bidirectional preference
(two-way choice).<br>
</div>
<div class="gmail-m_-4726504696247793351m_7433369598014388013moz-cite-prefix">from</div>
<div class="gmail-m_-4726504696247793351m_7433369598014388013moz-cite-prefix">Richard Lung.<br>
</div>
<div class="gmail-m_-4726504696247793351m_7433369598014388013moz-cite-prefix"><br>
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<div class="gmail-m_-4726504696247793351m_7433369598014388013moz-cite-prefix"><br>
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<div class="gmail-m_-4726504696247793351m_7433369598014388013moz-cite-prefix">On 20/12/2018 05:15, robert
bristow-johnson wrote:<br>
</div>
<blockquote type="cite">
<p><br>
<br>
---------------------------- Original Message
----------------------------<br>
Subject: [EM] IRV failure modes, vote splitting<br>
From: "John" <a class="gmail-m_-4726504696247793351m_7433369598014388013moz-txt-link-rfc2396E" href="mailto:john.r.moser@gmail.com" rel="noreferrer" target="_blank"><john.r.moser@gmail.com></a><br>
Date: Wed, December 19, 2018 10:34 pm<br>
To: <a class="gmail-m_-4726504696247793351m_7433369598014388013moz-txt-link-abbreviated" href="mailto:election-methods@electorama.com" rel="noreferrer" target="_blank">election-methods@electorama.com</a><br>
--------------------------------------------------------------------------<br>
<br>
> [I'm not subscribed, so please CC me on responses]<br>
><br>
> After looking at Burlington, VT 2009, I've started to ask
some questions<br>
> about IRV.<br>
<br>
what were you looking at? this, from Warren Smith?:</p>
<p> <a class="gmail-m_-4726504696247793351m_7433369598014388013moz-txt-link-freetext" href="https://rangevoting.org/Burlington.html" rel="noreferrer" target="_blank">https://rangevoting.org/Burlington.html</a></p>
<p>It's a good analysis. don't let this excellent analysis of the
Burlington 2009 get conflated with all of Warren's claims about
Score Voting or Approval Voting.</p>
<p>also
(other people on this list know this), i am a Burlington
resident (i happen to live in Bernie's ward), politically
active, and was there in 2009. at the time Andy Montroll was a
friend of mine.<br>
<br>
> I strongly prefer Tideman's Alternative Smith.</p>
<p>personally, i think that Tideman Ranked Pairs (using margins)
is just better. and it's simpler.</p>
<p><br>
> IRV eventually reduces to a three-way race, and I see some
interesting<br>
> things occur there.<br>
><br>
> In Plurality, you can add a candidate on the same
ideological end as your<br>
> opponent—if your opponent is more-liberal than you, then
add another<br>
> more-liberal opponent—and you split the vote. This lets you
win a close<br>
> race when you can't get majority.<br>
><br>
> In IRV, you also need to add a candidate, and the same
rules kind of work.<br>
> By adding a conservative to a two-liberal race, you siphon
votes from your<br>
> moderate (winning) opponent.</p>
<p>well, yes, but most of the moderate liberal voters had marked
the more liberal as their second choice and also the reciprocal.</p>
<p><br>
> That happened in 2009: Bob Kiss loses; add Kurt Wright and
Kurt Wright<br>
> wins plurality, Montroll has the fewest votes and is
eliminated, Kiss beats<br>
> Wright and wins.</p>
<p>Andy had the fewest 1st-choice votes of the three, but he was
the 2nd-choice of most of Kurt's voters and nearly all of Bob's
voters.</p>
<p><br>
><br>
> Interesting thoughts.<br>
><br>
> In the three-way race, it looks like Plurality without
Majority elects the<br>
> Condorcet loser. Kurt Wright lost to both Kiss and
Montroll,</p>
<p>in a pair-wise comparison, yes. loses to Andy by 929 votes and
lost to Bob by 252 votes (out of nearly 9000).<br>
<br>
> and didn't<br>
> have a majority. Lacking a majority, pulling the center
candidate would<br>
> tend to favor your opponent. This is because Conservatives
will roughly<br>
> split between two Conservatives; Liberals will roughly
split between two<br>
> Liberals; and so the three-way race necessarily has an
imbalance whereby<br>
> there are more Conservatives or more Liberals, and so a
split vote<br>
> resulting in no majority winner implies that there are more
of the group<br>
> splitting the vote.</p>
<p>i would put it more simply: if there *is* a single-dimensional
political spectrum from left to right, the center candidate is
far more likely to be preferred as a 2nd-choice to the voters on
the extremes than the candidate at the opposite extreme. both
GOP
voters and Prog voters selected the Dem candidate as their
second choice. </p>
<p><br>
> The plurality winner is smaller than this group, and<br>
> so is the Condorcet loser.<br>
><br>
> That's a logical outcome, not a mathematical one. We can
construct<br>
> situations where the liberals abandon the more-liberal
candidate for the<br>
> conservative; that's not likely in practice.<br>
><br>
> As per vote splitting, above, this three-way situation
would tend to take<br>
> votes from the more-center candidate. The more-center
candidate would be a<br>
> second choice for both ends, and so typically has
overwhelming support<br>
> against each candidate WHEN THERE IS NO MAJORITY WINNER.</p>
<p>well, we need to define exactly what we mean by a "majority
winner". if there are three or more candidates it's possible no
single candidate gets majority support. but between any pair of
candidates, there is a
majority winner unless they tie.</p>
<p>that's all Condocet does. just pairs the candidates with all
possible pair combinations and says consistently, "If more
voters mark their ballots preferring Candidate A to Candidate B
than voters marking the contrary, then Candidate B is not
elected." that simple rule pretty much defines Condorcet. and
the problem in Burlington 2009 was 587 more voters marked their
ballots that they preferred Andy over Bob than the number of
voters preferring Bob over Andy, yet Bob was elected.</p>
<p><br>
> That suggests IRV provides no real advantage in the
three-way race:<br>
</p>
<p>IRV doesn't do too bad in a 3-way race if one of those three
has far less support than the other two. but in Burlington
2009, all three had approximately equal support. the Prog was
the IRV winner, the GOP was the FPTP winner, and the centrist
Democrat was the Condorcet
winner. any of those three were a plausible winner.</p>
<p>i don't know of another governmental race using Ranked-Choice
Voting (what they now call it) where the method failed to elect
the Condorcet winner. but i think it will happen again.</p>
<p>When the spoiler has virtually no chance
in winning (but a good chance of spoiling), IRV will choose the
same as the Condorcet. it's only when there are 3 or more
plausible contenders that this hiccup happens.</p>
<p> </p>
<p>> - If Plurality isn't a Majority, IRV falls to
vote-splitting and never<br>
> elects the Condorcet candidate, but avoids the Condorcet
loser.<br>
><br>
> - If Plurality IS a Majority, IRV elects THE SAME CANDIDATE
as Plurality,<br>
> providing no advantage over Plurality in a three-way race.
That candidate<br>
> is the Condorcet candidate.<br>
><br>
> - When encountering a three-way Smith Set, Tideman's
Alternative Smith is<br>
> identical to IRV after eliminating all non-Smith
candidates.<br>
><br>
> These are, again, practical outcomes, not mathematical
ones.<br>
><br>
> IRV's single advantage over Plurality appears to be that it
mathematically<br>
> avoids the Condorcet loser, although when doing so it
practically<br>
> eliminates the Condorcet winner.</p>
<p>no it doesn't. not most of the time. </p>
<p>again, Burlington 2009 is the only governmental election using
RCV i am aware of in which the single-transferable vote method
failed to elect the Condorcet winner. I think all of the other
RCV
elections have.</p>
<p>but that's still not a good reason to use IRV over a
Condorcet-compliant method.</p>
<p>there are at least 4 solid reasons why IRV failed in Burlington
in 2009. the most important is that it failed to resist a
spoiler. because of that, a promise to the voters that
IRV made: that they would not need to vote tactically, they
could serve their political interests well by voting for their
favorite first, and marking their second favorite second. but
1500 Wright voters found out that, simply by marking their
favorite as #1, they caused the election of Bob
Kiss, where, if they had been tactical, they could have
insincerely bumped Kurt down a notch and let Andy rise to the
top and they would have prevented their lowest choice from
winning. it promised this spoiler thing would not happen.</p>
<p><br>
--<br>
<br>
r b-j <a class="gmail-m_-4726504696247793351m_7433369598014388013moz-txt-link-abbreviated" href="mailto:rbj@audioimagination.com" rel="noreferrer" target="_blank">rbj@audioimagination.com</a><br>
<br>
"Imagination is more important than knowledge."<br>
</p>
<p> </p>
<p> </p>
<p> </p>
<br>
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