[EM] A few concluding points about SFC, CC, method choice, etc.

[Chris Benham]

Pasting from Mike's page:

> /Some definitions useful in subsequent criteria definitions:/
>
> A voter votes X over Y if he votes in a way such that if we count only 
> his ballot, with all the candidates but X & Y deleted from it, X wins.
>
> [end of definition]
>
> Voting a preference for X over Y means voting X over Y. If a voter 
> prefers X to Y, and votes X over Y, then he's voting a sincere 
> preference. If he prefers X to Y and votes Y over X, he's falsifying a 
> preference.
>
> A voter votes sincerely if he doesn't falsify a preference, and 
> doesn't fail to vote a sincere preference that the balloting rules in 
> use would have allowed him to vote in addition to the preferences that 
> he actually did vote.
>
> [end of definition]
>
>
>     Strategy-Free Criterion (SFC):
>
> /Preliminary definition: /A "Condorcet winner" (CW) is a candidate 
> who, when compared separately to each one of the other candidates, is 
> preferred to that other candidate by more voters than vice-versa. Note 
> that this is about sincere preference, which may sometimes be 
> different than actual voting.
>
>
>     SFC:
>
> If no one falsifies a preference, and there's a CW, and a majority of 
> all the voters prefer the CW to candidate Y, and vote sincerely, then 
> Y shouldn't win.
>
> [end of definition]
>



Michael Ossipoff wrote:

> Kevin and Chris posted their criteria that they incorrectly claimed 
> equivalent to SFC.
>
> These same alternative "SFCs" have been posted to EM before and 
> thoroughly discussed before.
> In fact, we've been all over this subject before. 


So why don't you point us to where in the EM archive we can find this 
earlier discussion?  Are they in your opinion equivalent for
ranked-ballot methods?

> Though Chris's and Kevin's criteria clearly are not equivalent to SFC, 
> maybe someone could write a votes-only cirterion that is. First of 
> all, what's this obsession about "votes-only"?

Some people worry that criteria that give the appearance that we have to 
read voters' minds to see if they are met are not the easiest to check for.

> Now, quite aside from that,  the efforts to write a votes-only 
> equivalent criterion seem motivated by a desire to not say  things 
> that happen to be what I want to say. I want SFC to be about the fact 
> that that majority, because they all prefer the CW to Y, and because 
> there's no falsification (on a scale sufficient to change the 
> outcome), can defeat Y by doing nothing other than voting sincerely.
>
> To say it in a way that doesn't say that wouldn't be SFC. If someone 
> wrote such a criterion, then I'd recognize it as a _test_ for SFC 
> compliance, but not as SFC. When I say that a method passes or fails 
> SFC, and someone says "What's that?", then I want to tell them the SFC 
> described in the paragraph before this one, the one that relates to 
> the CW,  no need for other than sincere  voting by the majority and 
> non-falsified voting by everyone else. If I worded it like Kevin or 
> Chris, it wouldn't be self-evident why it's desirable to meet that 
> criterion.
>
> Someone could suggest that I use an alternative as the criterion, and 
> save my SFC as a justification. No, I want the criterion's value to be 
> self-evident.


Well its value as something distinct from the Condorcet  criterion isn't 
self-evident to me. If  this CW>Y majority can't elect the CW, why do 
they necessarily
care if  Y is elected or not?  

And the way you've dressed this up, I can't see how it really qualifies 
as a  "strategy criterion". How are the members of this CW>Y majority 
supposed to
know whether or not anyone "falsifies a preference"?  And if they do 
know what are they supposed to do about it?

 From Steve Eppley's MAM page:
     

>         /truncation resistance/ 
> <Proof%20MAM%20satisfies%20Minimal%20Defense%20and%20Truncation%20Resistance.htm>: 
> Define the "sincere top set" as the smallest subset
>         of alternatives such that, for each alternative in the subset, 
> say x, and
>         each alternative outside the subset, say y, the number of 
> voters who
>         sincerely prefer x over y exceeds the number who sincerely 
> prefer y
>         over x.  If no voter votes the reverse of any sincere 
> preference regarding
>         any pair of alternatives, and more than half of the voters 
> rank some x in
>         the sincere top set over some y outside the sincere top set, 
> then y must
>         not be elected. (This is a strengthening of a criterion having 
> the same name
>         promoted by Mike Ossipoff, whose weaker version applies only when
>         the sincere top set contains only one alternative, a Condorcet 
> winner.)


This makes some sense as a strategy criterion, being about deterring a 
faction from truncating against the members of the sincere
Smith set. The "weaker version" ascribed to you seems easier to test for.

How does that version differ from your present SFC?

Chris  Benham


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