On 12/14/2012 06:12 PM, Richard Fobes wrote:
On 12/13/2012 11:31 AM, Kristofer Munsterhjelm wrote:
On 12/13/2012 05:28 PM, Chris Benham wrote:
Of the various proposed ways of weighing "defeat strengths" in
Schulze, Losing Votes is the one that elects most from the "tops of
the ballots". Given that we are seeking to convert supporters of FPP
(and to I hope a lesser extent, IRV), I think that is a marketing
advantage.
On the other hand, we know that only paying mind to the tops of the
ballots is a bad idea. That's what Plurality does. IRV pays less
attention to the top (so that it can pass mutual majority, for
instance), but Australia and Burlington seem to indicate it's not enough
unlike Plurality.
In a sense, IRV pays too much attention to the "bottom of the ballot".
First, consider that plurality voting assumes that the candidate with
the _most_ first-choice votes is most popular.
Relatedly, IRV assumes that the candidate with the _fewest_ first-choice
votes is least popular.
Well, it still pays attention to the top of the ballot. It just derives
a different metric from the top of the ballot: a measure of how bad
something is, rather than of how good something is.
The reasoning is more indirect, so IRV passes things like mutual
majority. In a way it's similar to how Nanson and Baldwin's logic is
more indirect than Borda (upon which they are based), so that Nanson and
Baldwin passes majority and Condorcet but Borda does not.
Both beliefs are mistaken rather often.
IRV works fine if there are only two dominant candidates and other minor
candidates, but what's the point of adopting a better ballot if the
counting method only allows two main candidates?
Of course long-time folks here know all this, but there are a few folks
here who are in the process of learning more about voting methods.
There are people on this list who like IRV or think it's not too bad, so
I won't put words in their mouths. It feels a bit like IRV is an
incremental upgrade to Plurality, though, like someone sat down and
tried to find out how to solve Plurality's most obvious problem (minor
no-hopes interfering with the outcome). IRV does solve that most obvious
problem, but whether intentional or not, the patch doesn't extend far
enough: another problem appears when the parties grow to the size where
they're no longer no-hopes.
Yet the feeling can be deceiving. Knowing IRV's actual history, I don't
think someone sat down to patch Plurality. STV came first, and STV
*does* work. In STV with many seats, the Droop proportionality criterion
(DPC) makes sure that there's at least some measure of representation,
and as the number of seats increases, the leeway within DPC decreases,
so there's less of a chance for it to go wrong.
Then a certain organization decided that getting IRV for single-winner
elections would be a good stepping stone to STV. The rest, we all know :-)
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