[EM] IRV vs. plurality

[Kevin Venzke]

Eric,

Sorry, my message wasn't as clear as it could've been.

 --- Eric Gorr <eric at ericgorr.net> a écrit : 
> >>>     40 A
> >>>     35 C > B
> >>>     30 B
> >
> >>  The example given by Eric is not that realistic ( it is not likely you would
> >>  see such a vote set in a real election)
> >
> >If indeed this example is not realistic, it's because C decided
> >not to run lest he spoil the election and throw it to A.
> 
> Is it really not realistic?
> 
> It seems to me that it can easily be generated in 
> genuine elections when there are three or more 
> parties capable of getting first place votes.

Yes.  What I was aiming at was: if IRV were in place, then the C voters would 
have incentive to betray favorite; anticipating this, candidates like C would see 
less value in running at all.

> 
> >This incentive (for C to not run, and B voters to not vote for C) is the first
> >reason why I find IRV unacceptable.
> 
> There is also an incentive for the C voters to 
> vote insincerely and rank B first since they may 
> know their candidate cannot win.

Excuse me, that is what I was trying to refer to.  Actually if B-first voters like 
C somewhat, they could of course rank C second.

> 
> >  > and in the normal course of discussion I would probably counter
> >>  it with my favourite 49 A>B>C, 3 B>A>C, 48 C>B>A example with
> >>  some comment about the importance of first preference
> >>  votes/utility,
> >
> >But evidently you find such a scenario as unlikely as the
> >Condorcet supporters do.
> 
> But, I really don't understand this scenario, assuming voters voted sincerely.
> 
> It is clear that the unambiguous winner is B. 
> This is very different from the example above, 
> where B should be the winner, but A won the 
> election.

I hear you.  I suppose the response is, "Utility is important, and the first rank
is the only one that threatens to tell us anything about utility."  Myself, I don't
see IRV as the solution to this concern, particularly if there's favorite-betrayal
incentive!

Kevin Venzke
stepjak at yahoo.fr


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