[EM] Condorcet-Approval hybrid method

[Kevin Venzke]

Russ,

 --- Russ Paielli <6049awj02 at sneakemail.com> a écrit : 
> Or perhaps you think you 
> gain some strategic advantage by ranking them equal -- which is 
> precisely one reason I lean toward disallowing it.

You can get an advantage, but it isn't free. So I think when voters
want to use equal ranking, it probably makes the result better than if
they can't.

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.

(Incidentally, this also works in the CDTT method I suggest. The CDTT
is {a,b,c} at first; when the B>C voters rank B=C, the CDTT becomes
just {c}.)

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.

If you didn't allow equal ranking, the B>C voters would either be out
of luck, or they would have to realize that voting C>B>A or perhaps
just "C" is what it takes to get their compromise choice instead of 
their last choice.

Kevin Venzke



	

	
		
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