[EM] St. Louis and Pushover (Re: Reply to Rob regarding RCV)

[C.Benham]

Kristofer,

> Do you think that my example:
>
> /B>A>C>D>E>F>X //leads A to win, but ////B>A>X>C>D>E>F ////leads B to win. /
> is an instance of pushover? If so, there may be ranked methods that fail
> it even though they're monotone, and the problem isn't limited to rated
> methods alone.

To be honest I haven't been thinking about Push-over as something only 
about ballots and
outcomes, independent of voter intentions based on their knowledge of of 
how the voting
algorithm works.

But if forced to limit myself to defining it in terms of ballots and 
outcomes, then my answer is
yes (but with more information, maybe not "definitely yes").

If, given how the algorithm works and the voter's knowledge of it and 
his knowledge or correct
guesses about how others voted he could reasonably expect that raising X 
in that way would change
the winner to one he more prefers, and that's the only reason he did it; 
then obviously the voter
has used  a pushover strategy.

But at the other extreme, if he just sincerely changed his mind about X, 
and as far as he knew that
was not likely to change the result regarding any non-X candidates or if 
it was possible for that to
happen it was just as likely to be in a direction he didn't like as one 
he did; then I'd say the voter
voted sincerely and was just lucky.

Chris B.

>
>
> *Kristofer Munsterhjelm*km_elmet at t-online.de 
> <mailto:election-methods%40lists.electorama.com?Subject=Re%3A%20%5BEM%5D%20St.%20Louis%20and%20Pushover%20%28Re%3A%20Reply%20to%20Rob%20regarding%20RCV%29&In-Reply-To=%3C50156fc9-db6b-7916-328f-f8cd71da21af%40t-online.de%3E>
> /Mon Oct 2 03:49:30 PDT 2023/
> ------------------------------------------------------------------------
> On 10/2/23 07:07, C.Benham wrote:
> >/Kristofer, />//>/What does "IIRC" mean? /
> If I Recall Correctly.
>
> >//>>/I can see two ways to interpret pushover. The definition from />>/Electowiki is: />>//>>/"Push-over is a type of tactical voting that is only useful in methods />>/that violate monotonicity. It may involve a voter ranking or rating an />>/alternative lower in the hope of getting it elected, or ranking or />>/rating an alternative higher in the hope of defeating it." />//>/Courtesy of someone (I'm sure a promoter of STAR) Electowiki has been />/made much worse (IMHO) than it used to be, and so is now not great. />//>/The older definition you helpfully recovered from Condorcet.org : />>/*push-over* />>/The strategy of ranking a weak alternative higher than one's preferred />>/alternative, which may be useful in a method that violates />>/monotonicity />>/<https://web.archive.org/web/20090713234702/http://www.condorcet.org:80/emr/defn.shtml#monotonicity>. 
> />>/*monotonicity* />>/The property of a method where an alternative can never be made to />>/succeed by being ranked lower on some ballots.  Doing this is using />>/the "push-over />>/<https://web.archive.org/web/20090713234702/http://www.condorcet.org:80/emr/defn.shtml#push-over>" 
> strategy. />//>/I think this old Blake Cretney definition is right if we assume strict />/ranking ballots (i.e. no above-bottom equal-ranking allowed). />//>>/A strict interpretation considers "defeating it" to mean "turn the />>/candidate from winning to no longer winning". />//>/No, I think it is about raising a "weak" candidate in order to "defeat />/it" (and thereby win the election) instead of losing to a stronger />/candidate in the final decisive part />/of the election process. />//>/You seem to be right about STAR meeting mono-raise.   I suspect that the />/Electowiki entry is an attempt to define Push-over in such a way that it />/can't be a problem for STAR. /
> I don't know if it's intentionally made more vague to support STAR.
> Believing in ignorance before malice, I would just assume it's just a
> vague definition.
>
> Do you think that my example:
>
> >>/B>A>C>D>E>F>X />>//>>/leads A to win, but />>//>>/B>A>X>C>D>E>F />>//>>/leads B to win. /
> is an instance of pushover? If so, there may be ranked methods that fail
> it even though they're monotone, and the problem isn't limited to rated
> methods alone.
>
> -km
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