[EM] POLL: References (was Re: Poll, preliminary ballots)

[Chris Benham]

Kristofer,

> It also seems to define the criterion a bit differently:
>
>>> If a majority prefers one particular candidate to another, then they
>>> should have a way of voting that will ensure that the other cannot win,
>>> without any member of that majority reversing a preference for one
>>> candidate over another.
>
> which would indicate that the majority can bar a particular candidate 
> from winning by voting in some given way that does not involve order 
> reversal, only truncation.

"Truncation" or equal-ranking.  Steve Eppley a while back had a 
"Non-Drastic Defense" criterion that says that if more than half the 
voters vote A over B and A no lower than equal-top then B can't win.

You'd think everything would meet that, but Margins doesn't.

Of course Double Defeat (met by ASM and Smith//Approval and Double 
Defeat,Hare of the methods nominated in our current poll) implies easy 
compliance with the criterion you quote.

If A has a pairwise win over B, then the A>B preferring voters (whether 
they are a "majority" or not) can ensure that B doesn't win by approving 
A and not approving B.

The Double Defeat feature is both a common-sense way of tending to make 
for a higher social utility winner and an easy common-sense "defensive 
strategy" device.

Chris B.

On 15/05/2024 4:06 am, Kristofer Munsterhjelm wrote:
> On 2024-05-14 19:55, Michael Ossipoff wrote:
>> It seems to me that the Weak Defensive Strategy Criterion was a 
>> generalization of FBC:
>>
>> One should never get a worse result because they didn’t vote 
>> something they like less over something they like more.
>>
>> Strictly-speaking, Condorcet methods fail, but wv Condorcet doesn’t 
>> fail importantly. Most other Condorcet methods fail badly, because 
>> they fail FBC badly.
>>
>> I don’t expect Benham to either, though wv is all that I’ve tested.
>
> https://electowiki.org/wiki/Weak_Defensive_Strategy_criterion says 
> that Schulze passes.
>
> So does 
> http://lists.electorama.com/pipermail/election-methods-electorama.com/2000-April/102004.html
>
> It also seems to define the criterion a bit differently:
>
>>> If a majority prefers one particular candidate to another, then they
>>> should have a way of voting that will ensure that the other cannot win,
>>> without any member of that majority reversing a preference for one
>>> candidate over another.
>
> which would indicate that the majority can bar a particular candidate 
> from winning by voting in some given way that does not involve order 
> reversal, only truncation.
>
> If there's a sincere CW, then it's the same as your criterion, but if 
> not, then there may be one majority who prefers A to B and another 
> that prefers A to C, but no majority preferring A to both B and C. 
> Then the majority preferring A to B should have a way to stop B from 
> winning...
>
> I think? It's not my criterion.
>
> -km
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