[EM] Chris: Approval vs IRV

[MIKE OSSIPOFF]

Chris said:

Stephane,
I  also rate IRV  above Approval, for many reasons. For a method to be
acceptable to me, it must meet  Majority for solid coalitions (Woodall
calls "Majority" and  others call  "Mutual Majority")  and  Clone
Independence(Woodall's  Clone-winner and Clone-loser
criteria).

I reply:

Fair enough. Then, for you, IRV is better than Approval. For you, by your 
chosen criteria.

You continue:

Common-sense, Mike O. and I  agree that  Approval fails Clone
Independence.  Some may sneer, but these criteria are
easy to meet; and failing them allows  all sorts of  unfairness and
absurdity.

I reply:

But IRV had no unfairness & absurdity? :-) Specifics are always better than 
namecalling.

You continued:

To my mind, Approval does NOT satisfy Independence of Irrelevant 
Alternatives (IIA)

I reply:

IIAC has more conflicting definitions than any other criterion. I'm sure you 
can dream-up one that Approval fails. Whether you can meaningfully define 
it, so that not every method fails it, is another matter.

Approval meets the popular brief IIAC definition that has been posted to EM 
by various people with a few equivalent wordings:

Deleting a losing candidate from the ballots, and recounting those ballots, 
shouldn't change who wins.


You needn't prove that Approval doesn't meet ICC. That's common knowledge on 
EM.

You continued:

One of my fundamental standards is that a method should perform reasonably 
when all the voters
vote sincerely (taking no account of how any other voters might vote).

I reply:

IRV fails your standard in the most flagrant and ridiculous ways. This has 
been very well-described on EM, even in recent weeks, and so don't ask me to 
repeat the examples. Aside from the recently-posted example, there's also 
the absurd nonmonotonicity of IRV, even when people vote sincerely.

Actually, IRV is at its very worst when people vote sincerely. Often the CW 
can be saved only be the extreme insincere strategy of favorite-burial.

You continued:

A method should be able to cope with insincerity, but to perform reasonably 
it definitely shouldn't
DEPEND on insincerity."

I reply:

Like when, in IRV, the election of a CW depends on voters insincerely voting 
the CW in 1st place, over their genuine favorite?

You continue:

Isn't that enough "unfairness and absurdity"?

I reply:

Definitely.

You continue:

I agree that "defensive srategy citeria" are valuable, but the starting 
point should be that the
method is, and appears to be, fair and sensible if all the voters vote 
sincerely.

I reply:

As I said, IRV fails that standard of yours.

You continued:

Approval is based on the assumption that all the voters strategise, and in 
effect invites them to
do so; because it doesn't even give voters who have a strict ranking and who 
want to vote sincerely
a clear-cut instruction on how to do so.

I reply:

Yes, in Approval the strategy need can't be ignored. In IRV, you can ignore 
it, and then be hit in the face by it when your last choice wins because you 
didn't bury your favorite.

And the strategy needed in Approval never requires favorite-burial.

You continued:

Instead it leaves them wondering why they should "vote for"
more than one candidate, and if they should, then how many more.

I reply:

...just as IRV leaves you wondering if you should vote Compromise in 1st 
place, burying Favorite, so that Worst won't win.

You continued:

Approval would be less unacceptable if the ballot instruction was at least 
concise and semi-sensible.
Either "Check the candidates you rank in equal-first place. Barring 
candidtes you rate as unacceptable,
check the other candidates you rate as above-average in this field", or the 
simpler "Of these
candidates, check those you rate as above average".

I reply:

Fortunately you won't be writing the balloting instructions for Approval.

"Vote for 1 or more" is sufficient for the instruction on the ballot.

The ballot instruction needn't be a strategy suggestion. Strategy 
suggestions can be found elsewhwere, as at http://www.electionmethods.org

, at the Approval Strategy pages. Or in a recent posting of mine to EM. 
Political orgnizations and parties would be distributing strategy 
suggestions, and the government could do so also, but there's no need for it 
to actually be on the ballot.

You continued:

But according to Approval advocates that I've been in contact with, there 
definitely shouldn't be
"strategy advice" on the ballot paper. Oh no, there should just be the 
infuriatingly meaningless
"Vote for" whichever candidates you choose.

I reply:

The ballot paper doens't have room to name all the strategies that could be 
used in Plurality or Approval, let alone explain them. And IRV strategy? 
Forget it. I don't know if anyone has studied it. Runoff strategy is much 
more complicated than Approval stratgegy, requiring many more summations and 
estimates of probabilities. IRV strategy would be Runoff strategy to the Nth 
power. Yes, explain that on the IRV ballot paper :-)

You continued:

Another thing I hate about Approval is that elections in the US are 
apoltical enough as it is.In
election campaigns, voters should be thinking about politics, and the 
policies and qualities of
the candidates. Approval would help get rid of that, by turning the election 
into a kind of sport
between rival factions of strategising voters.

I reply:

It isn't entirely clear why you believe that strategy would get rid of 
concern about policies and qualities of the candidates. Those things would 
determine how people rate the candidates, which would be important in 
determining people's voting.

You continued:

Tv debates and newspaper articles could be all about
"what is the best Approval voting strategy?".

I reply:

The best Approval strategy for you is crucially based on how good you 
believe the candidates are. In 2004, I suggest that the best Approval 
strategy for progressives would be to vote only for Nader, given the 
existing candidate lineup.  Likewise in Plurality. (At this time we don't 
have reliable winnability or tie-probability information, so it makes sense 
to use 0-info strategy, or to experimentally vote only for the best).

You continued:

Also of course, obsessing about polls will be
intensified. Maybe everytime a new poll is published, tv reporters will ask 
Mike Ossipoff "What does
this new poll mean for voters who want to maximise the effect of their 
vote?"

I reply:

That would be great if they did, referring to the polls in the media.  I'd 
say, "Nothing, because the value of a poll depends on the honesty and 
motives of those who report the results. It's a 0-info election."

Of course there could  be polls taken by people or organizations that are 
trusted by progressives, and that would be different. Then there'd be 
reliable polling information for progressives.

You continued:

And of course voters who succeed in ignoring this circus and instead just 
concentrate on the
policies and qualities of the candidates, will potentially be greatly 
disadvantaged (much more than
a "naive", sincere IRV voter).

I reply:

When you say that voters who base their voting on the merits of the 
candidates will be disadvantaged in Approval, that shows that you are 
completely uninformed about Approval. With any method that requires 
strategy, that strategy is based on predictive information and sincere 
ratings. With Condorcet, one is most free of need for strategic voting, as 
we here  have defined it. With Approval & IRV, you need strategic voting. 
But with IRV that strategic voting that you need will sometimes require 
burying your favorite.

Mike Ossipoff

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