[EM] Equal-ranking in Condorcet, SCRIRVE (was" Condorcet-Approval hybrid method")

[Kevin Venzke]

Chris,

 --- Chris Benham <chrisbenham at bigpond.com> a écrit : 
> "Suppose we're using a WV method:
> 
> 40 A>B>C
> 35 B>C>A
> 25 C>A>B
> 
> There's an A>B>C>A cycle. B>C is the strongest win (75 votes), followed
> by A>B (65 votes) and C>A (60 votes). So C>A is discarded and A wins.
> 
> But suppose the B>C voters see this coming and perhaps don't feel
> as strongly between B and C. They might instead vote B=C>A. When
> that happens, there is still a cycle, but now B>C is the weakest win
> with only 40 votes. Now C wins.
> 
> I don't consider that the B>C voters get this advantage for free. In
> order for it to work, they have to give up the opportunity to distinguish
> between B and C."
> 
> Those last two sentences are just putting a bizarre spin on rewarding 
> indecisiveness. Suppose those B=C voters
> (in the modified example) really are too stupid and lazy to decide which 
> they prefer out of B and C, they just hate A.
> Then they *are* "getting an advantage for free"!

I guess lazy and stupid voting could sometimes be beneficial.

> Based on the sincere rankings, what possible case is there that electing 
> C is  "better" than electing A?  In this classic
> 3-candidate cycle scenario, if the method meets Majority then there are 
> always voters with an incentive to Compromise.
> Based on these particular sincere rankings, I can't see that we really 
> have any guide as to which is the "best" winner other than the
> Borda scores, and C is the big Borda loser (having the fewest 
> first-preferences and the most last-preferences)!

The sincere rankings are irrelevant since you can't make people cast sincere
votes. If we assume that the voters are not stupid and lazy, and just rank 
candidates equally when there isn't a large utility gap (or, when they're 
concerned about cycle resolution), then the cast votes will give us an indication 
of how much the voters care about each preference. If a voter says, "I'd rather 
take B or C and up the odds that A loses, rather than try to insist on B over C,"
that tells us something.

Kevin Venzke



	

	
		
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