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

[Richard Lung]

On 24/05/2019 12:43, Richard Lung wrote:
> With FAB STV, a blank ballot returned means NOTA (without privileging 
> that particular preference perm on the ballot paper) and counts as one 
> vote towards a quota for leaving an empty seat. Any partially blank 
> vote of preferences also counts to a less extent against a seat being 
> filled. This procedure establishes absolute preference for the 
> candidates as a whole, not just relative preference between them.
> You would indeed have to tell the voters in advance the consequences 
> of their being remiss in filling in all the preferences!
>
> from
> Richard Lung.
>
> On 24/05/2019 00:24, Stéphane Rouillon wrote:
>> 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 <mailto: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 <mailto:rbj at audioimagination.com>
>>>
>>> "Imagination is more important than knowledge."
>>>
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>>
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>

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