[EM] How to describe RAV/ARC
Forest Simmons
simmonfo at up.edu
Tue Mar 15 14:12:08 PST 2005
On Tue, 15 Mar 2005, Ted Stern wrote:
> I don't think
> anybody could argue with that.
Bart inoculated me against ever using that sentence :')
Here's my sales pitch (to EM members) for RAV/ARC:
When candidate X beats Y in both approval and by head-to-head choice,
let's say that X strongly beats Y.
If X strongly beats Y then both approval and pairwise methods agree that Y
should not win.
What happens if we eliminate all of the candidates that are strongly
beaten?
The remaining candidates form a set P that are totally ordered by the
ordinary pairwise beat relation.
The top of this totally ordered chain is the RAV/ARC winner.
That ends my EM sales pitch for RAV/ARC. [I would use a different pitch
for the general public.]
But now let me continue on to a sales pitch for a related method:
We got the set P by eliminating all of the candidates that both Approval
and Condorcet agree should be eliminated.
The remaining candidates are the subjects of irreconcilable disagreement:
As we noted above, they are totally ordered by by the ordinary pairwise
beat relation, but I forgot to mention that they are also totally ordered
by approval order.
That would be fine except that these two orders are diametrically opposed;
one is the exact reverse of the other.
In other words the set P is the set of candidates on which approval and
Condorcet have irreconcilable disagreement.
Any unbiased compromise between Approval and Condorcet must give each
member of P a chance of winning.
Random ballot from P results in a fair chance that is monotonic and clone
proof.
Forest
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