[EM] SARC definition improvement

[MIKE OSSIPOFF]

> > Your sincere ranking is ABC
> >
> > 100 voters: ABC
> > 99 voters: BAC
> >
> > Without you, A wins.
> >
> > Then you show up, and, believing that B needs your vote against C,
> > you vote BAC. Now B wins. You've defeated your favorite by voting
> > an undefeated strategy.
>
>How do you interpret this example showing Borda violates SARC?
>

Borda violates SARC because you voted an undominated strategy,
and you thereby caused your favorite to lose.

>Do you say "It is a problem that this additional voter is punished
>for showing up and using an offensive strategy. An election method

No. I don't consider that voter to have used an offensive
strategy. In that example you tried to help a compromise whom
you believed you needed, and that isn't what I'd call offensive
strategy. The need to do things that could act against your
interest in order to help a compromise--that's the lesser-of-2-
evils problem that I've referred to on this list.

In that example,
what I consider a problem is when you can defeat your favorite
because you felt it necessary to help a compromise.

If you've given away the election by defeating your favorite
when he had a win, it's because you were voting insincerely to
help a compromise.

Often, with most voting systems, protecting a compromise
involves insincere voting. But no one ever votes a dominated
strategy, and it would be nice to be able to say that, with
a particular voting system, someone who votes an undominated
strategy (meaning anyone, anytime) won't defeat his favorite or
elect his last choice.

With Approval that can be said.

[Do I believe that an election method...]
>should guarantee that a given voter never worsens the result of
>the elections (due to his sincere preferences) by showing up
>independently on whether this voter votes sincerely or uses a
>defensive strategy or uses an offensive strategy."? Or do you

No. For one thing, SARC limits itself to the defeat of your
favorite, & the election of your last choice, rather than
, in general, worsening your outcome. SARC says that a voter
who votes an undominated strategy (as everyone always does)
shouldn't defeat his favorite or elect his last choice. I consider
that a desirable property. Of course there's nothing in SARC that
refers to sincere, insincere, or strategic voting. However, in
practice,  SARC failure happens when you vote insincerely
as a strategy to help a compromise, and you defeat your favorite.

Incidentally, in IRV you can make your last choice win without
even voting insincerely, because you showed up instead of staying
home. So SARC badexamples aren't limited to sincere or
insincere voting.

[Do I...]
>say "It is not a problem that this additional voter is punished
>for showing up and using an offensive strategy. The fact that a

I don't say that it's not a problem that that voter showed up
and used an offensive strategy. I don't say he used an offensive
strategy. I _do_ say that what happened is a problem, because he
gave away his favorite's win by helping a compromise that he
believed he needed. That kind of voting is a real problem here,
and we don't know how many wins are being given away. Maybe
Nader has a win, and all the fearful, cowed people voting
for Gore are giving the election away. Do I consider that a problem?
Yes. November 2000 might well be a SARC badexample.

[The fact that a...]
>given voter can worsen the result of the elections (due to his

No, SARC isn't about general worsening of one's outcome. It's
specifically about defeating one's favorite or electing one's
last choice.

>sincere preferences) by showing up and using an offensive strategy
>deters this voter from using an offensive strategy."?

I don't agree that an offensive strategy was used in the example.
In any case, SARC doesn't say anything about strategy, though
insincere voting is what causes the violations. But no,
a motivation to protect offensive strategizers from being deterred
is not my reason for proposing SARC.

You ask about a SARC violation deterring insincere voting. That
would be nice if it did, and I wish that voters had a concern
about that in November 2000, and that that concern would deter
insincere voting. But regrettably, we can't expect that. So no,
deterrence due to SARC violation or possible SARC violation isn't
a problem that concerns me. The problem is that insincere
voting--compromise in particular--can and does make people's favorite
lose.

By the way, how's this for a brief Participation wording?:

Adding to the count some identical ballots that vote X over y
shouldn't change the winner from X to Y.

Mike Ossipoff


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