<div dir="auto">Thanks for the experiment. I hope that Tideman’s organization won’t be promoting the old margins version of RP. …unless just for maybe choosing between pizza-toppings or movies.</div><div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Sep 20, 2023 at 07:30 Colin Champion <<a href="mailto:colin.champion@routemaster.app">colin.champion@routemaster.app</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div>
<font face="Helvetica, Arial, sans-serif">Well, I coded up
Minimax(WV) for my own evaluation. Rather to my disgust (and
contrary to Darlington) I find that it does indeed outperform
Margins for truncated sincere ballots. I ran a large number of
trials with 10001 voters under a spatial model, 8 candidates being
truncated to 4. Minimax (margins)=83.35% correct,
minimax(wv)=84.09%. Other methods which outperformed standard
minimax in the simulation include Approval Sorted Margins (in an
ordinal version suggested by Ted Stern): 84.14%; Black: 84.22%;
Smith,Borda: 84.22%. <br>
Hastily written and unreliable code, not to be trusted. <br>
CJC<br>
</font></div><div><br>
<div>On 18/09/2023 22:30, Michael Ossipoff
wrote:<br>
</div>
<blockquote type="cite">
<div dir="auto">Hi Colin—</div>
<div dir="auto"><br>
</div>
<div dir="auto">Yes, margins beats wv for social-utility under
sincere voting when there’s that vanishingly rare natural
top-cycle.</div>
<div dir="auto"><br>
</div>
<div dir="auto">But Darlington & Tideman evidently aren’t
considering resistance to offensive strategy, which is a much
bigger threat than natural top-cycles.</div>
<div dir="auto"><br>
</div>
<div dir="auto">Protecting the CW from offensive strategy is more
important than SU in natural top-cycles.</div>
<div dir="auto"><br>
</div>
<div dir="auto">…& is better for SU.</div>
<div><br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Mon, Sep 18, 2023 at
07:03 Colin Champion <<a href="mailto:colin.champion@routemaster.app" target="_blank">colin.champion@routemaster.app</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div> <font face="Helvetica, Arial, sans-serif">Thanks to
Kevin and Michael for pointing out a feature of minimax
I was unaware of. I had however seen Richard
Darlington's paper [1] in which he referred to 'several
studies' comparing margins with winning votes. He
reports that margins 'was the big winner in all of
them'. I suppose I'll have to look deeper.<br>
Colin<br>
[1]. <a href="https://arxiv.org/abs/1807.01366" target="_blank">https://arxiv.org/abs/1807.01366</a><br>
</font></div>
<div><br>
<div>On 18/09/2023 07:57, Michael Ossipoff wrote:<br>
</div>
<blockquote type="cite">
<div><br>
</div>
<div><br>
<div class="gmail_quote" dir="auto">
<div dir="ltr" class="gmail_attr">----------
Forwarded message ---------<br>
From: <strong class="gmail_sendername" dir="auto">Michael
Ossipoff</strong> <span dir="auto"><<a href="mailto:email9648742@gmail.com" target="_blank">email9648742@gmail.com</a>></span><br>
Date: Sun, Sep 17, 2023 at 22:54<br>
Subject: Re: [EM] Ranked Pairs<br>
To: Forest Simmons <<a href="mailto:forest.simmons21@gmail.com" target="_blank">forest.simmons21@gmail.com</a>><br>
</div>
<div class="gmail_quote" dir="auto"><br>
</div>
This was meant to be sent by “Reply All”, in order
to post it. So now I’m forwarding it to EM.<br>
<br>
<div dir="auto">Forest—</div>
<div dir="auto"><br>
</div>
<div dir="auto">But wv prevents truncation
(strategic or otherwise) from taking the win from
a CW.</div>
<div dir="auto"><br>
</div>
<div dir="auto">…&, with, wv, refusing to rank
anymore you don’t approve will cause offensive
order-reversal by their preferrers to backfire.</div>
<div dir="auto"><br>
</div>
<div dir="auto">I’d always take that precaution,
& would advise others to.</div>
<div dir="auto"><br>
</div>
<div dir="auto">When we discussed these guarantees
years ago they seemed absolute, & we still
have the guarantee-criteria based on them…met by
wv versions of MinMax, RP, CSSD, &
Smith//MinMax.</div>
<div dir="auto"><br>
</div>
<div dir="auto">…&, with MinMax, whose winner
can come from anywhere, not just from the
top-cycle, & so, offensive order-reversal,
when there are a fair number of candidates, is
unpredictable & risky for its perpetrators,
even if the precaution of deterrent-truncation
isn’t taken.</div>
<div><br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sun, Sep
17, 2023 at 21:17 Forest Simmons <<a href="mailto:forest.simmons21@gmail.com" target="_blank">forest.simmons21@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)">
<div dir="auto">
<div><br>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On
Sat, Sep 16, 2023, 9:42 PM Michael
Ossipoff <<a href="mailto:email9648742@gmail.com" target="_blank">email9648742@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)">
<div dir="auto">Is that RP(wv), or
RP(margins) ?</div>
<div dir="auto"><br>
</div>
<div dir="auto">RP(wv) would thwart
& deter offensive strategy, an
important property in public
elections.</div>
<div dir="auto"><br>
</div>
<div dir="auto">…&, actually, it
seems to me that MinMax(wv) would do
that better.</div>
<div dir="auto"><br>
</div>
<div dir="auto">That’s because,
choosing only from the Smith Set RP,
limits it’s choice to the strategic
top-cycle that created by the
offensive strategists.</div>
<div dir="auto"><br>
</div>
<div dir="auto">Suppose that the CW’s
preferrers don’t do defensive
truncation (never rank anyone you
wouldn’t approve in Approval, or
whose preferrers you regard as
likely to offensively order-reverse)
?</div>
<div dir="auto"><br>
</div>
<div dir="auto">Knowing that RP will
limit its choice to their small
strategic top-cycle, it would be
easier for the strategists to be
fairly sur that their candidate
would win in that top-cycle.</div>
<div dir="auto"><br>
</div>
<div dir="auto">But, with MinMax, the
winner is chosen more broadly, &
could be anywhere in the
candidate-set. …making it more
difficult & risky to confidently
do offensive order/reversal.</div>
<div dir="auto"><br>
</div>
<div dir="auto">RP(margins) might the
best choice for a completely honest
electorate, but MinMax(wv) seems
better for public elections, due to
its better thwarting &
deterrence of offensive strategy.</div>
<div dir="auto"><br>
</div>
<div dir="auto">Yes, MinMax doesn’t
meet the luxury cosmetic look-good
criteria that RP meets. </div>
<div dir="auto"><br>
</div>
<div dir="auto">But for one thing, I
remind you that natural ( sincere)
top-cycles are vanishingly-rare.</div>
</blockquote>
</div>
</div>
<div dir="auto"><br>
</div>
<div dir="auto">This is the same conclusión
I have come around to. </div>
<div dir="auto"><br>
</div>
<div dir="auto">And methods that break a
three member top cycle at the weakest link
tend to reward the burier faction.</div>
</div>
<div dir="auto">
<div dir="auto">
<div class="gmail_quote">
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)">
<div dir="auto"><br>
</div>
<div dir="auto">So do you want to have
less strategy-protection, in order
for the result to maybe look better
in a vanishingly rare natural
top/cycle?</div>
<div dir="auto"><br>
</div>
<div dir="auto">…& how bad is a
violation of Condorcet-Loser anyway.
“Beaten by all the other
alternatives” sounds like some kind
of unanimity, but of course it
isn’t. It isn’t like a
Pareto-violation. I remind you that
the MinMax winner has fewer voters
preferring some particular candidate
over him than anyone else does.</div>
<div dir="auto"><br>
</div>
<div dir="auto">Clone-Criterion
violation? How bad that really in
MinMax, especially when we’re
talking about a vanishingly rare
natural top-cycle?</div>
<div dir="auto"><br>
</div>
<div dir="auto">RP(margins) for a
completely honest electorate.</div>
<div dir="auto"><br>
</div>
<div dir="auto">MinMax(wv) for public
elections.</div>
<div dir="auto"><br>
</div>
<div dir="auto">..& about a
primary to reduce the candidates to
5: Forget the primary. If you think
people will have trouble
rank-ordering lots of candidates, I
remind you that, to vote among them
in a primary, they’d still have to
examine & choose among the
initial many candidates.</div>
<div dir="auto"><br>
</div>
<div dir="auto">…harder than ranking
only the ones you know & regard
as deserving & definitely in
your accepts& preferred set.</div>
<div dir="auto"><br>
<div class="gmail_quote" dir="auto">
<div dir="ltr" class="gmail_attr">On
Wed, Sep 13, 2023 at 00:18 Colin
Champion <<a href="mailto:colin.champion@routemaster.app" rel="noreferrer" target="_blank">colin.champion@routemaster.app</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204,204)">I
notice that RP is the only
election method mentioned by
name in the <br>
Virginia agenda.<br>
<br>
A while ago I ran some
simulations on elections with
truncated ballots. <br>
Something I noticed was that the
presence of RP in the list of
methods <br>
made the software unacceptably
slow. I didn't look into the
cause, but <br>
there's a natural explanation,
which is the fact that RP is
known to be <br>
NP-complete when it deals
correctly with tied margins,
i.e. by <br>
exhausting over all their
permutations. Presumably if some
candidates <br>
are unpopular and ballots are
extensively truncated, then tied
margins <br>
are much likelier than with
complete ballots.<br>
<br>
I gather that practical
implementations of RP choose a
random <br>
permutation rather than
exhausting. This seems to me to
bring a danger. <br>
The presence of a few vanity
candidates (truncated off almost
all <br>
ballots) may lead to ties, and
this may lead to a comfortable
winner <br>
looking as though he owes his
victory to a coin-toss.
Obviously this <br>
undermines the legitimacy of his
win.<br>
<br>
CJC<br>
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