On 09/30/2012 11:47 AM, Juho Laatu wrote:
On 30.9.2012, at 11.56, Kristofer Munsterhjelm wrote:
In practice, that means: is cloneproof, passes independence of as
much as possible (independence of Smith-dominated alternatives,
say), and is monotone.
These criteria could be one set of definitions of a good (sincere)
winner. I usually do not assume the first two ones since there may be
good (sincere) winners also outside those criteria. Monotonicity is
maybe more natural in the Condorcet category.
There might be, but then again, there may also be better outcomes when
the method does not get confused by vote-splitting problems (e.g. the
Korean election).
Maybe one could say:
- Good outcome under honesty to start with something reasonable,
- protection against the method getting lost on its own or being
deceived, and
- assurance that the method doesn't behave in a way that robs the result
of legitimacy,
which would be the categories in reverse order.
I've put strong in quote marks because I know others may disagree
with my priorities. FairVote obviously doesn't consider the "having
weird result dynamics" part important as long as the strangeness
can't be exploited by deliberate strategy.
If one looks positively at their criteria, maybe they put strong
emphasis on the marketability of the method. That marketability may
include some tendency to favour the large parties.
That, or they play a long game that involves getting the voters used to
IRV so they can then slip in STV.
In my opinion, even if that works, it won't have the desired effect.
Australia shows this.
The second is resistance to noise and strategy. Independence of
clones fit here, as well as independence of X (Smith-dominated
alternatives, Pareto-dominated alternatives, weak IIA). The
resistance may protect against strategy - cloneproof methods keep
parties from running an army of identical candidates - or improve
the outcome when there is no strategy - e.g. by not being affected
by the liberal parties' vote-splitting in a replay of the 1988
South Korean presidential election.
(I just note that independence of clones can be an interesting topic
both when discussing behaviour with sincere votes and strategies.)
Right. I don't think Tae-woo plotted to have Young Sam and Dae-jung
split the liberal vote. Nor do I think the Republicans funneled funds to
Nader in 2000. Thus I'd call that noise rather than strategy, though
perhaps "noise" doesn't really fit, either.
The third is quality of the outcome under honesty, according to
some metric or desired logic. It's hard to say which metric one
should pick, unfortunately, and for Ranked Pairs (and Schulze),
there's probably no simple metric that the method optimizes.
Furthermore, the logic one uses for rated methods probably wouldn't
directly fit onto rank methods (because utilities are either
unknown or not applicable).
It seems that I assumed above that this category and the first
category are related. Maybe this category implies also the first
category. I.e. there is no such good logic of what we desire that
would break against the first caregory. (Or maybe, if we step outside
the Condorcet domain and think about IRV, then maybe the idea of
kicking the weakest candidate out at every round makes sense in some
setup??)
Say you had a method that was independent of covered alternatives, and
this method otherwise optimized similarly to Range - i.e. would tend to
pick the uncovered candidate with best mean Range score on all possible
Range elections that you could transform the current ranked election
into. This might satisfy the third category from a utilitarian point of
view, and the second (by its independence of covered alternatives).
However, it would fail the first because ICA implies nonmonotonicity.
So the difference between the third and first category is, I think, that
the third is about what's good for society in general, while the first
is about what makes the voters (and candidates) accept the outcome. The
more democracy is about having the losers accept that they've lost, the
more important the first category becomes with respect to the third, for
instance.
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