[EM] Defeat strength, Winning Votes vs. Margins, what to do with equal-ranks on the ballot?

[Richard Lung]

On 24/05/2019 12:59, Richard Lung wrote:
> In theory, FAB STV is an RCV system that is based on keep values, as 
> operated by Meek Method STV. The difference is that the former system 
> gives keep values for unelected, as well as elected, candidates. 
> Elected candidates have keep values of one or less. So, candidates 
> with no votes or preferences whatsoever would have keep values of 
> infinity.
> This is not so bad as it sounds. In fact it makes no difference to the 
> counting procedure. If you wanted to avoid the infinities, then 
> candidates would be allowed to vote for themselves, ensuring a minimum 
> one vote. This would give the candidate a keep value that is the same 
> as the value of the quota (being the quota divided by one vote).
>
> from
> Richard Lung.
>
> On 24/05/2019 00:30, robert bristow-johnson wrote:
>>
>> I think all unranked candidates are tied for last place, no? Are 
>> there any variants of RCV that this is different?
>>
>> Whether equally-ranked candidates are counted as votes for *both* 
>> candidates or for *neither* candidates cannot make a difference for 
>> Margins.  But it seems to me that it makes a difference if Winning 
>> Votes is the measure of defeat strength.
>>
>> regrads,
>>
>> r b-j
>>
>>
>>
>> ---------------------------- Original Message 
>> ----------------------------
>> Subject: Re: [EM] Defeat strength, Winning Votes vs. Margins, what to 
>> do with equal-ranks on the ballot?
>> From: Stéphane Rouillon <stephane.rouillon at sympatico.ca>
>> Date: Thu, May 23, 2019 4:24 pm
>> To: rbj at audioimagination.com
>> Cc: election-methods at lists.electorama.com
>> --------------------------------------------------------------------------
>>
>> > All criterias (Winning Votes, Margins, Relative Margins) have 
>> advantages and are acceptable. The fine choice depends on the 
>> interpretation you told voters that would be made of blank ballots. 
>> If a blank rank means "all bad", WV is perfect. If it means "all the 
>> same" Margin is good, and if it means "I don't know but I trust other 
>> voters to express a valid opinion about this option", then RM is 
>> perfect. Just tell voters the chosen interpretation of blank tanks in 
>> advance so they can fill a sincere ballot...
>> >
>> > Envoyé de mon iPhone
>> >
>> >> Le 22 mai 2019 à 20:18, robert bristow-johnson 
>> <rbj at audioimagination.com> a écrit :
>> >>
>> >>
>> >> i'm posting this to the list. i hope it's okay.
>> >>
>> >> i had been asked:
>> >>
>> >> > This "plausible example" you can think of, why don't you show it 
>> to us?
>> >>
>> >> i'm not as good as you guys in dreaming up the number of ballots 
>> ranked however:
>> >>
>> >> ex. A>B>C>D
>> >>
>> >> but could you have a defeat matrix where
>> >>
>> >> A>B>C
>> >>
>> >> but C>A by a smaller defeat strength than A>B or B>C. But D>A by 
>> an even smaller defeat strength, however D<B and D>C?
>> >>
>> >> i dunno how to dream up ballot combinations to do that.
>> >>
>> >>
>> >> > Without it all I can say that is that the River winner may or 
>> may not be
>> >> > a "better choice" than the
>> >> > RP winner.
>> >> >
>> >> > River's main practical point is that it easier than Schulze and 
>> RP to use.
>> >>
>> >> i think it's more complicated than RP. it's RP with an additional 
>> exception.
>> >>
>> >>
>> >>
>> >> i have to say i am still not convinced of WV. probably 
>> Schulze-Margins is still the best, but RP-Margins good enough and 
>> possibly easier to sell to policy makers and the public.
>> >>
>> >> i like Margins in principle: The percentage Margin is 
>> (WV-LV)/(WV+LV) and is a measure of the decisiveness of defeat, 
>> without respect to the size of the election. So 5% defeat is a more 
>> decisive defeat than a 4% defeat.
>> >>
>> >> But if you consider every Condorcet pair as it's own little 
>> election, then the salience of the election would be the number of 
>> voters that weigh in on it, which is WV+LV.
>> >>
>> >> So if the net defeat strength (the index to rank the pairs) is the 
>> product of how important the election is with the decisiveness of 
>> defeat you get:
>> >>
>> >> (WV+LV) x (WV-LV)/(WV+LV) = WV - LV
>> >>
>> >> it just seems to me that Margins is better than WV.
>> >>
>> >> but say, WV, is a good idea for defeat strength. is LV a better idea?
>> >>
>> >> hmmmm.
>> >>
>> >> --
>> >>
>> >> r b-j rbj at audioimagination.com
>> >>
>> >> "Imagination is more important than knowledge."
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >> ----
>> >> Election-Methods mailing list - see https://electorama.com/em for 
>> list info
>> >
>>
>>
>> --
>>
>> r b-j rbj at audioimagination.com
>>
>> "Imagination is more important than knowledge."
>>
>>
>> ----
>> Election-Methods mailing list - seehttps://electorama.com/em  for list info
>
>

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