[EM] Dave on approval, ranked ballots

[Kevin Venzke]

Dave,

> Please give an example, but:
>       No IRV - let that be a separate project.
>       No cycles - likewise, unless you state that there is no problem 
> without cycles being involved.

When no cycles are involved, Condorcet is 100% perfect. So I have to use
examples with cycles:

--- Dave Ketchum <davek at clarityconnect.com> a écrit :
> >>My comparison of methods:
> >>      Approval - its backers like to brag, but it is not that simple - 
> >>unlike Condorcet and IRV, voters CANNOT say:  I prefer Nader but, only if 
> >>I cannot have Nader, give me Kerry as better than Bush.
> > 
> > However, ranked methods won't always obey your request. Condorcet methods
> > and IRV will both sometimes take the vote "Nader>Kerry>Bush" and elect Bush,
> > when if you had instead not ranked Nader, the method would elect Kerry. That
> > is, the method ignores the fact that you said "If I cannot have Nader, give
> > me Kerry."

77 A>B>C
57 B>C>A
145 C>A>B
143 C=B>A
80 A>B>C

WV methods elect C. But if the 80 A>B>C voters instead lower A anywhere below
B, then the winner is B. So the methods ignore these voters' wish that B be elected 
if they can't get A.

> > Condorcet methods will sometimes see the "give me Kerry as better than Bush"
> > part and give the win to Kerry, when it could have gone to Nader otherwise,
> > despite the fact that your vote says "ONLY if I cannot have Nader, give me
> > Kerry."

On these ballots:
49 Bush
24 Kerry>Nader>Bush
27 Nader>Kerry>Bush

WV methods (actually, all Condorcet methods) elect Nader. But if the 24 voters 
just vote "Kerry," with no preference for Nader, then the winner is Kerry. So
the methods ignore the 24 voters' request that they get Nader ONLY if they
can't have Kerry.

My point is that, at least with approval voting, the voter knows the limits of
how the method will use his ballot. With ranked ballots one can't be sure that
the method won't pick and choose what information to use, or even (in the
first example) use the information to elect the ballot's last choice.

Kevin Venzke



	

	
		
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