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

[Kristofer Munsterhjelm]

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