On Sat, Sep 16, 2023, 9:42 PM Michael Ossipoff email9648742@gmail.com
wrote:

This is the same conclusión I have come around to.

And methods that break a three member top cycle at the weakest link tend
to reward the burier faction.

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.
Colin
[1]. https://arxiv.org/abs/1807.01366

On 18/09/2023 07:57, Michael Ossipoff wrote:

---------- Forwarded message ---------
From: Michael Ossipoff email9648742@gmail.com
Date: Sun, Sep 17, 2023 at 22:54
Subject: Re: [EM] Ranked Pairs
To: Forest Simmons forest.simmons21@gmail.com

This was meant to be sent by “Reply All”, in order to post it. So now I’m
forwarding it to EM.

Forest—

But wv prevents truncation (strategic or otherwise) from taking the win
from a CW.

…&, with, wv, refusing to rank anymore you don’t approve will cause
offensive order-reversal by their preferrers to backfire.

I’d always take that precaution, & would advise others to.

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.

…&, 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.

On Sun, Sep 17, 2023 at 21:17 Forest Simmons forest.simmons21@gmail.com
wrote:

Election-Methods mailing list - see https://electorama.com/em for list info

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info

Hi Colin—

Yes, margins beats wv for social-utility under sincere voting when
there’s that vanishingly rare natural top-cycle.

But Darlington & Tideman evidently aren’t considering resistance to
offensive strategy, which is a much bigger threat than natural top-cycles.

Protecting the CW from offensive strategy is more important than SU in
natural top-cycles.

…& is better for SU.

On Mon, Sep 18, 2023 at 07:03 Colin Champion
<colin.champion@routemaster.app
mailto:colin.champion@routemaster.app> wrote:

 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.
    Colin
 [1]. https://arxiv.org/abs/1807.01366
 <https://arxiv.org/abs/1807.01366>

 On 18/09/2023 07:57, Michael Ossipoff wrote:

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 Election-Methods mailing list - see https://electorama.com/em
 <https://electorama.com/em> for list info

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%.
Hastily written and unreliable code, not to be trusted.
CJC

On 18/09/2023 22:30, Michael Ossipoff wrote:

Hi Colin—

Yes, margins beats wv for social-utility under sincere voting when there’s
that vanishingly rare natural top-cycle.

But Darlington & Tideman evidently aren’t considering resistance to
offensive strategy, which is a much bigger threat than natural top-cycles.

Protecting the CW from offensive strategy is more important than SU in
natural top-cycles.

…& is better for SU.

On Mon, Sep 18, 2023 at 07:03 Colin Champion <
colin.champion@routemaster.app> wrote:

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info

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.

On Wed, Sep 20, 2023 at 07:30 Colin Champion <
colin.champion@routemaster.app> wrote:

Election-Methods mailing list - see https://electorama.com/em for list
info

I think that if you were looking at the success rates of unilateral
burial options along with the basic burial defense of truncation below
sincere CW ... then the difference between Winning Votes and Margins
would be more striking (still in favor of wv).

On Wed, Sep 20, 2023, 2:12 PM Michael Ossipoff <email9648742@gmail.com
mailto:email9648742@gmail.com> wrote:

 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.

 On Wed, Sep 20, 2023 at 07:30 Colin Champion
 <colin.champion@routemaster.app
 <mailto:colin.champion@routemaster.app>> wrote:

     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%.
        Hastily written and unreliable code, not to be trusted.
           CJC

     On 18/09/2023 22:30, Michael Ossipoff wrote:

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     <https://electorama.com/em> for list info

 ----
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 <https://electorama.com/em> for list info

Hi Colin,

Le vendredi 22 septembre 2023 à 02:57:42 UTC−5, Colin Champion colin.champion@routemaster.app a écrit :

I am not sure what to make of Darlington's defeat strength comparison. It sounds like
it was basically a simulation of sincere voters who vote equality because they actually
consider the candidates equal. That premise is fine but somewhat far removed from how
this topic is usually discussed, i.e. with some consideration of comparative strategy.

I notice incidentally that Darlington says incorrectly on page 22 that MinMax(PO) is a
Condorcet method. I wonder whether he implemented it as one to get his numbers on that.

In any case:

To find the motivation for WV I would start with first principles. How should we design
a Condorcet completion method to minimize strategic incentives? A motivation behind
Condorcet itself is that voters should not vote sincerely only to find that they
should've voted another way.

What could this mean here? Well, a full majority can always get what they want by
changing their votes. Therefore if a majority votes A>B yet B is elected, we have
probably done something wrong, because the majority certainly did have the power to
make A win instead. The election of B gives the A>B voters an incentive to vote
differently to change the outcome. The voters obtain a "complaint," I will call it.
Since majorities will most predictably obtain such complaints when we override their
preference, we should prioritize locking majorities.

With WV, there is no special heed paid to majorities, it just goes down the list of
contests starting with the largest winning blocs. But this achieves the goal. It
applies its principle to sub-majority contests as well, and maybe this is good bad or
neutral, but maybe we can believe that if it was helpful (for our end goal) to favor
majorities over sub-majorities then it could also be helpful to favor larger
sub-majorities over smaller sub-majorities. It certainly stands to reason that the more
voters you have sharing some stance, the more likely it is that a vote change on their
part could change the outcome.

(On my website I describe a different approach focused on compromise incentive, and
measuring the potential for this more directly, and one can take that as me suggesting
that WV actually leaves some room for improvement.)

You notice that adding half-votes to equal rankings under WV will turn it into margins.
This would give every contest a full majority on the winning side, and seemingly we can
trivialize this requirement of mine to prioritize majorities.

But I think it's clear, in the context of this analysis, that adding half-votes for
equal rankings doesn't make sense. The voter who says A=B doesn't turn into a pair of
opposing "half-complaints," where one of the complaints has the potential to be voiced
when either of A or B is elected. The A=B voter has no possible complaint either way,
as neither result can incentivize them to change their vote.

Additionally, I think that voters expect and want it to be the case that abstaining
from a pairwise contest does not mean the same thing as saying they rate both
candidates equal. I touched on this in my previous post.

Consider this election:

7 A>B
5 B
8 C

Margins elects A, which is very unusual across election methods, and I think most
people would find this result surprising due to a sense of what truncation ought to
mean.

(Consider copying it into votingmethods.net/calc to see margins and MMPO stand alone
here.)

Perhaps with enough education people can understand that the method takes seriously
the apparent equality of the truncated preferences. But I don't think voters will find
it comfortable to vote under those circumstances. I think voters want to be able to
identify the set of candidates that they believe they are trying to defeat, leave them
out of their ranking, and not have to think any further about it.

Kevin
votingmethods.net

  Hi Colin,

Le vendredi 22 septembre 2023 à 02:57:42 UTC−5, Colin Champion colin.champion@routemaster.app a écrit :

I am not sure what to make of Darlington's defeat strength comparison. It sounds like
it was basically a simulation of sincere voters who vote equality because they actually
consider the candidates equal. That premise is fine but somewhat far removed from how
this topic is usually discussed, i.e. with some consideration of comparative strategy.

I notice incidentally that Darlington says incorrectly on page 22 that MinMax(PO) is a
Condorcet method. I wonder whether he implemented it as one to get his numbers on that.

In any case:

To find the motivation for WV I would start with first principles. How should we design
a Condorcet completion method to minimize strategic incentives? A motivation behind
Condorcet itself is that voters should not vote sincerely only to find that they
should've voted another way.

What could this mean here? Well, a full majority can always get what they want by
changing their votes. Therefore if a majority votes A>B yet B is elected, we have
probably done something wrong, because the majority certainly did have the power to
make A win instead. The election of B gives the A>B voters an incentive to vote
differently to change the outcome. The voters obtain a "complaint," I will call it.
Since majorities will most predictably obtain such complaints when we override their
preference, we should prioritize locking majorities.

With WV, there is no special heed paid to majorities, it just goes down the list of
contests starting with the largest winning blocs. But this achieves the goal. It
applies its principle to sub-majority contests as well, and maybe this is good bad or
neutral, but maybe we can believe that if it was helpful (for our end goal) to favor
majorities over sub-majorities then it could also be helpful to favor larger
sub-majorities over smaller sub-majorities. It certainly stands to reason that the more
voters you have sharing some stance, the more likely it is that a vote change on their
part could change the outcome.

(On my website I describe a different approach focused on compromise incentive, and
measuring the potential for this more directly, and one can take that as me suggesting
that WV actually leaves some room for improvement.)

You notice that adding half-votes to equal rankings under WV will turn it into margins.
This would give every contest a full majority on the winning side, and seemingly we can
trivialize this requirement of mine to prioritize majorities.

But I think it's clear, in the context of this analysis, that adding half-votes for
equal rankings doesn't make sense. The voter who says A=B doesn't turn into a pair of
opposing "half-complaints," where one of the complaints has the potential to be voiced
when either of A or B is elected. The A=B voter has no possible complaint either way,
as neither result can incentivize them to change their vote.

Additionally, I think that voters expect and want it to be the case that abstaining
from a pairwise contest does not mean the same thing as saying they rate both
candidates equal. I touched on this in my previous post.

Consider this election:

7 A>B
5 B
8 C

Margins elects A, which is very unusual across election methods, and I think most
people would find this result surprising due to a sense of what truncation ought to
mean.

(Consider copying it into votingmethods.net/calc to see margins and MMPO stand alone
here.)

Perhaps with enough education people can understand that the method takes seriously
the apparent equality of the truncated preferences. But I don't think voters will find
it comfortable to vote under those circumstances. I think voters want to be able to
identify the set of candidates that they believe they are trying to defeat, leave them
out of their ranking, and not have to think any further about it.

Kevin
votingmethods.net