[Election-Methods] RE : Re: RE : Re: Re: rcv ala tournament

Dan Bishop danbishop04 at gmail.com
Sun Dec 30 23:51:18 PST 2007

Kevin Venzke wrote:
> Hi,
> (Responses to Juho and Dan)
> --- Juho <juho4880 at yahoo.co.uk> a écrit :
>> Kevin, you maybe already know/guess my answer. B is only 2 votes  
>> short of being a Condorcet winner. C would need 3 and A 5 votes.
>> In your comments I note that you may think that listing a candidate  
>> (higher than default bottom) has a special meaning. If there is  
>> something like an implicit approval cutoff after the listed  
>> candidates (=> 7 B>C>>A, 5 C>>A=B, 8 A>>B=C) then that should be  
>> explicitly mentioned. The used method could in this case count both  
>> the pairwise preferences and the approvals (A and C would be more  
>> approved than B), and the result could be something different than  
>> with pure ranking based ballots.
> I think WV agrees with the voter's nature more. In Margins if the
> frontrunners are A and B, and there are a bunch of other poor candidates, I
> may be expected to explicitly rank the worse frontrunner in second place in
> order to stop my vote from being credited to random people.
> In WV I can abstain from those contests and thereby weaken their
> importance. I don't think voters want to have to explicitly vote for the
> worse of two frontrunners, and I don't think when they leave him and others
> off they wish that this part should be filled out randomly.
> (I say "randomly": On average randomly has the same effect.)
> --- Dan Bishop <danbishop04 at gmail.com> a écrit :
>> * If truncated ballots were disallowed and people flipped coins to 
>> decide between the bottom-ranked candidates, then B wins with a 
>> probability of 43.19%, compared to 30.51% for C and a mere 0.45% for A.
>> * Margins makes more intuitive sense than Winning Votes.  The latter is 
>> equivalent to assuming that the people who didn't vote a preference 
>> between two candidates would have unanimously voted for the pairwise 
>> loser.  The former is equivalent to assuming that they'd split their 
>> vote equally between the two, which is MUCH more likely.
> Can you explain how WV is "equivalent to assuming that the people who
> didn't vote a preference between two candidates would have unanimously
> voted for the pairwise loser"? Do you mean "...winner"?
No, I mean loser.  Under WV, the following are equivalent:

A>B: 51
A=B: 49

A>B: 51
B>A: 49
> To my mind, the theory behind WV is that a contest is more decisive the
> more people that participate in it. Only you mustn't count the voters on
> the losing side, because they could then regret expressing their opinion
> rather than indifference.
This is where we disagree.  In my view, a unanimous contest with 30% 
turnout is more decisive than a 51%-49% contest with 60% turnout, 
despite the fact that the latter had more votes for the winner.
> >From the WV perspective one could say that margins is equivalent to
> treating unspecified preferences as aiming simply to increase the effect of
> those contests on the outcome.
>> But I see no justification for automatically assuming that "ranked" 
>> means "approved".
> How is there less justification to interpret an explicit marking for a
> candidate as a type of "approval," than to interpret the unspecified
> preferences as explicit indifference, and using this implied explicit
> indifference to elect candidates?
Because it's plausible that voters would rank a candidate they dislike 
over a candidate they dislike even more.  The B>C voters might really 
prefer B>>C>A (for example, B (100) > C (25) > A (0)).  But clearly, 
they should cast a B>C vote to keep A from getting elected.
> Note that WV doesn't actually do the former; it just doesn't violate
> criteria (or offend electorates) that do. It looks safer in that respect.
> If you take this election:
> 7 B>C
> 5 C
> 8 A
> And happened to know that the C and A voters *aren't* trying to use
> margins' auto-randomize feature, and were simply trying to express that
> they don't like the unranked candidates, then you wouldn't want to elect B.
> Now what is lost in the reverse situation (i.e. our voters are
> margins-inclined) if you elect C? Are A voters really going to throw a fit
> that their unspecified indifference didn't assist B?
> Kevin Venzke
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