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Daniel wrote:<br>
<br>
> Given a choice between two methods that are equally good in
other respects, I would pick the one where the best strategy is to
vote honestly. It's hard to trust that an otherwise good voting
method will produce good results if people are motivated to lie on
their ballots.<br>
<br>
This is a valid point. My own metric implicitly assumes that an
innocent error is neither more nor less serious than an error
induced by tactical voting. This is a reasonable starting position
but not ultimately tenable - ideally we'd want to weight the two
sorts of error differently, and recognise that providing people with
an incentive to vote dishonestly is an additional fault besides
getting the wrong result. But a weight of 0 for innocent errors is
even less tenable, and if we're to quote a single figure we can't
avoid adopting some implicit weight. <br>
<br>
In fact even innocent errors aren't really innocent. If a method
produces errors which aren't due to tactical voting, they're
probably due to the configuration of candidates, and therefore
provide perverse incentives to candidacy which in turn distort
political discourse. In the end I've been inclined to stick with
equal weighting while admitting that it needs a prominent health
warning, but this is partly because I've never seen the position
argued that tactical errors are more critical than innocent ones. <br>
<br>
On the magnitude of errors, my own figures suggest that
Condorcet/Hare makes fewer but larger errors than minimax when
confronted with false cycle tactics, and therefore looks marginally
better in terms of accuracy (and no doubt much better in terms of
strategy resistance) but significantly worse in terms of Euclidean
loss. See<br>
<a class="moz-txt-link-freetext" href="http://www.masterlyinactivity.com/condorcet/condorcet.html#results">http://www.masterlyinactivity.com/condorcet/condorcet.html#results</a><br>
(where Condorcet/Hare=Condorcet+AV).<br>
<br>
And on IRV... I don't favour it at all, but having condemned it for
its faults, I don't want to additionally condemn it for its few
merits, one of which is allowing a strategic escape from the centre
squeeze.<br>
<br>
CJC<br>
<br>
<div class="moz-cite-prefix">On 17/01/2022 09:31, Daniel Carrera
wrote:<br>
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cite="mid:CAEaabNiWOk+nTTS1aRHjPkQy5KY+h6fEFCHd=HzGeMKkyOfPjg@mail.gmail.com">
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<div class="gmail_default" style="font-family:trebuchet
ms,sans-serif;font-size:small"><span
style="font-family:Arial,Helvetica,sans-serif">On Mon, Jan
17, 2022 at 2:48 AM Colin Champion
<a class="moz-txt-link-rfc2396E" href="mailto:colin.champion@routemaster.app"><colin.champion@routemaster.app></a> wrote:</span><br>
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<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">A bit of a side question,
but is strategy resistance a good metric to quote?<br>
FIrstly, you'd never rank methods on it - you'd end up
choosing a <br>
coin toss.<br>
</blockquote>
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<div class="gmail_default"
style="font-family:"trebuchet
ms",sans-serif;font-size:small">It's not my #1
priority, but it seems pretty important to me. Given a
choice between two methods that are equally good in other
respects, I would pick the one where the best strategy is
to vote honestly. It's hard to trust that an otherwise
good voting method will produce good results if people are
motivated to lie on their ballots.</div>
<div class="gmail_default"
style="font-family:"trebuchet
ms",sans-serif;font-size:small"><br>
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<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
Secondly, voting methods recommended for their
resistance to <br>
tactical voting sometimes have the property that when they
go wrong, <br>
they make larger mistakes than those made by methods
targeting sincere <br>
voting. If you don't take this into account, you can draw
misleading <br>
conclusions.<br>
</blockquote>
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<div class="gmail_default"
style="font-family:"trebuchet
ms",sans-serif;font-size:small">Hmmm... I did not
know that. Can you give me an example? Yeah, that sounds
like something we'd really want to avoid.</div>
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<div> <br>
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<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">
Thirdly, consider a 3-candidate election using IRV. The
central <br>
candidate is the Condorcet winner, but supporters of one of
the <br>
non-central candidates realise that the opposed non-central
candidate is <br>
likely to win owing to the operation of a centre squeeze,
and therefore <br>
compromise on the central candidate. This satifies JGA's
definition of <br>
strategic manipulation but is certainly not an additional
fault in IRV; <br>
on the contrary, it's a mitigation of its weakness under
sincere voting.<br>
</blockquote>
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<div class="gmail_default"
style="font-family:"trebuchet
ms",sans-serif;font-size:small">That does sound like
a fault in IRV. If the goal is to get the Condorcet winner
(and I agree!) why not use a Condorcet method? The example
you cite is one of my biggest complaints with IRV. If
people are driven to vote dishonestly to compensate for a
failure of the system, that tells me that the method is
flawed.</div>
<div class="gmail_default"
style="font-family:"trebuchet
ms",sans-serif;font-size:small"><br>
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<div> </div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">My own practice has been
to measure the performance of methods in the <br>
presence of tactical voting exactly as I would in its
absence, simply <br>
skipping over any attempted manipulation which doesn't lead
to a worse <br>
result.<br>
</blockquote>
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<div class="gmail_default"
style="font-family:"trebuchet
ms",sans-serif;font-size:small">If two election
methods elect the same good candidate, but one of them
achieves that by letting people vote honestly and the
other requires people to learn that they need to
manipulate their votes... to me that seems like a relevant
difference.</div>
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<div class="gmail_default" style="font-family:"trebuchet
ms",sans-serif;font-size:small"><br>
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<div dir="ltr"><font face="trebuchet ms,
sans-serif">Dr. Daniel Carrera</font></div>
<div dir="ltr"><font face="trebuchet ms,
sans-serif">Postdoctoral Research
Associate</font></div>
<div><font face="trebuchet ms, sans-serif">Iowa
State University</font></div>
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