[EM] Re: Condorcet's strategy problem, ICA
robla at robla.net
Sat Sep 17 22:38:24 PDT 2005
On Sun, 2005-09-18 at 03:15 +0200, Kevin Venzke wrote:
> --- Rob Lanphier <robla at robla.net> a écrit :
> > My understanding is that FBC is mutually exclusive of the Condorcet
> > winner criteria. As I've stated above, when Condorcet winner is
> > violated, there's a good chance that one person, one vote has been
> > violated.
> > I will be willing to bet that there's some element of this problem in
> > any FBC complying method.
> What about Minmax(pairwise opposition), in which the winner is the candidate
> for whom the greatest number of votes against him in any contest is the
> smallest such score among all candidates?
> The change necessary to permit my ICA method to satisfy FBC sacrifices
> Condorcet hardly at all.
> This is Condorcet:
> "If there is one candidate who beats all the others, he must win."
> ICA satisfies this:
> "If there is one candidate who doesn't lose to any others after certain losses
> are disregarded (due to being reversible by voters using equal-top ranking),
> he must win."
> ICA scales Condorcet back only as far as is necessary to satisfy FBC.
Let's take a look at the example posted on the ICA page on Electowiki
( http://wiki.electorama.com/wiki/ICA ) (probably your example):
The head-to-head pairwise score in this election is 40-25 (35 abstain).
I don't like the idea of inferring that all of these voters "approved"
of B to declare B the winner. Those 40 voters would rightfully expect
that "A>B" be the same as saying "A", and would feel ripped off that
their 40 votes actually counted both for and against A in the A-B
comparison. They might also complain one person, one vote has been
violated, since their 40 votes for A over B don't count for as much as
the 25 votes for B over A. Actually, the 40 votes don't count at all.
My understanding based on your previous descriptions of ICA is that
explicit approval is problematic in ICA, since there's a lot of gaming
that can be done below the cut line.
All things considered, I'm not sure how this doesn't count as "favorite
betrayal". A voters gave the election away by "approving" B. Their
favorite (A) lost the election as the result of a lower ranking.
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