matt welland wrote:
On Mon, 2011-10-17 at 20:42 +0200, Kristofer Munsterhjelm wrote:
matt welland wrote:
Again, I think it is very, very important to note that the ranked
systems actually lose or hide information relative to approval in both
these cases.
In what manner does a ranked method hide information? Neither ranked
ballot methods nor strategic Approval can distinguish between
"everybody's equally good" and "everybody's equally bad".
Note that in the first case the results and impact of a ranked system
are actually worse than the results of approval. The political pressure
to converge and appeal to a broad spectrum is greater under approval
than the ranked systems. The evaluation of a voting system only makes
sense in the context of all the other things going on in a society. The
pressure on politicians to actually meet the needs of the people is a
massively important factor and ranked systems appear to wash out some of
that force which is a very bad thing IMHO.
Again, why is that the case? In Approval, you're either in or you're
out; but in ranked methods, the method can refine upon those two groups
and find the better of the good (be that by broad or deep support
relative to the others). If anything, this finer gradient should
increase the impact, not decrease it, because the search will more often
be pointed in the right direction.
A ranked system cannot give the feedback that all the candidates are
disliked (e.g. all candidates get less than 50% approval). It also
cannot feedback that all the candidates are essentially equivalent (all
have very high approval).
Neither does strategic Approval. In Approval, the best simple strategy
(if I remember correctly) is to approve the perceived frontrunner you
prefer, as well as every candidate who you like better. In a Stalin
election, if people were perfectly rational, the left-wingers would
approve Stalin if the other frontrunner was Hitler.
Well, perhaps people aren't perfectly rational. However, to the degree
they are honest, Approval can get into a contending third-party problem.
If you have a parallel universe where Nader is nearly as popular as
Gore, liberals would have to seriously (and strategically) think about
whether they should approve of Gore or not - if too many approve of Gore
*and* Nader, Nader has no chance of winning; but if too many approve of
only Nader, Bush might win.
Ranked systems essentially normalize the vote. I think this is a serious
issue. A ranked system can give a false impression that there is a
"favorite" but the truth might be that none of the candidates are
acceptable.
Some ranked methods can give scores, not just rankings. As a simple
example, the Borda count gives scores - the number of points each
candidate gets - as a result of the way it works. The Borda count isn't
very good, but it is possible to make other, better methods give scores
as well; and if you do so, an "equally good/equally bad" situation will
show as one where every candidate gets nearly the same score.
As for distinguishing "equally bad" from "equally good", there are two
ways you could do so within ranked votes. You could do it implicitly, by
assuming that the voters approve of the candidates they rank and
disapprove of those they don't; or you can do it explicitly by adding a
"against all" (re-open nominations, none of the below, etc) virtual
candidate.
Ironically by trying to capture nuances the ranked systems have lost an
interesting and valuable part of the voter feedback.
A voting system should never give the impression that candidates that
are universally loathed are ok. If our candidates were Adol Hitler,
Joseph Stalin, Pol Pot, Idi Amin, Benito Mussolini, Mao Zedong and
Leopold II of Belgium then approval would rightly illustrate that none
are good candidates. However a ranked system would merely indicate that
one of them is the "condorcet" winner giving no indication that none are
acceptable.
Here, an implicit solution would record heaps of blank votes, and an
explicit one would show the virtual candidate to be the CW.
I think any sane voting system *must* meet this requirement. The ability
for the electorate to unambiguously communicate that none of the
candidates are worthy of the post under contest.
I don't know how to prove it but my hunch is that approval would be more
resistant to manipulation by the so-called "one percenter" elites than
ranked systems.
James Green-Armytage's paper seems to show Approval as one of the rules
more vulnerable to strategic voting (see
http://www.econ.ucsb.edu/~armytage/svn2010.pdf ). Whether or not that
would translate into one-percenter manipulation, however, I don't know.
I suspect that most of the rules (e.g. various Condorcet methods,
Approval, Majority Judgement) would be sufficiently resistant. Even
top-two seems to do well enough to break Duverger's law.
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