On 07/10/2012 08:19 PM, robert bristow-johnson wrote:
On 7/10/12 6:51 AM, Kristofer Munsterhjelm wrote:
When runoffs are subjected to criterion analysis, one usually
considers voters to vote in the same order in each round. If they
prefer A to B in the first round,
now how is this known, without a ranked ballot?
It isn't. In the analysis, one imagines the voters having hidden
preferences (be they cardinal or ordinal), and the voters then vote
according to that preference as best as they're able.
For instance, if voter X has a hidden preference A>B>C>D, is honest, and
the system is top-two runoff, he'd vote A in the first round. If, say, B
and D go to the second round, he'd then vote for B.
and A and B remain in the second round, they'll vote A over B in the
second round.
that is, if nothing changes their mind. during our big IRV slugfest we
had in 2010 (as a consequence of the 2009 IRV election), one of the
points of the opponents of IRV was that they felt they deserved the
right to make up or even change their minds about A and B. even if they
voted for A or B in the first round.
i, of course, felt it is a reasonable requirement that voters make up
their minds about candidates by Election Day and that the downside of
delayed-runoffs exceed this nebulous "freedom to change my vote" that
the opponents touted. (one argument these folks made was that if their
favorite candidate was eliminated in the first round, these voters would
like to know who, of the remaining candidates in the runoff, their
candidate might favor. i still don't see that as a compelling argument
for delayed runoff.)
There are game-theory advantages to having multiple rounds. In an
exhaustive runoff, one can show there's an equilibrium where the honest
CW wins, for instance. This holds in the three-candidate case for
top-two runoff. The strategy involves the majority that prefers the CW
coordinating so that the CW is never eliminated in an earlier round, and
so is probably unrealistic, but it shows runoffs can do things
single-round rules can't.
This may not necessarily fit reality. Voters may leave or join
depending on whether the second round is "important" or not, and the
same for later rounds in exhaustive runoff.
and this can be adequately dealt with using a ranked ballot. as long as
all of the candidates are in the race up to Election Day, if it's
important enough to vote during *any* round, it's important enough to
rank it on a single ballot.
i know there is more to your post, Kristofer, but i have to decode more
of it before i can say anything about it. at least in my experience, all
non-IRV elections were either straight plurality, or had a top-two
runoff. and, besides the problem of greatly reduced turnout for the
runoff, it is not clear that the top-two vote getters should be the
candidates in the runoff. indeed, my argument to Democrats who voted
against IRV (to return us to plurality/runoff) is that the candidate who
should have won the 2009 race (who was the Dem candidate, so we Dems
felt screwed) would *not* have ended up in the delayed runoff, had that
been the law at the time. so voting against IRV and returning to delayed
runoff did nothing to solve that problem.
so i dunno how we do "better" delayed runoffs without using a ranked
ballot in the first round to begin with. and if you do that, then what's
the point (other than allowing voters to change their mind after
Election Day)?
The kind of systems I'm talking about would accept ranked ballots. The
runoffs would, apart from allowing voters to change their mind, also
protect against simple strategies. Say that the method is Condorcet and
enough people go on a burial spree to push the "honest" winner to second
place in the outcome. Then the runoff is still honest (majority rule is
strategy-proof), so the right candidate would win.
I suppose that furthermore, I'm thinking it could be useful to know
about better runoff rules in case Plurality's Duvergerian tendencies are
inherent to single-winner single-round methods in general. I don't think
it is actually so, but in case, being prepared about methods that do
work can't do harm :-)
We know that runoffs counter two-party rule to at least some extent,
because nations that use them tend to have multiparty rule whereas
nations with ordinary Plurality don't -- and while IRV has superior
criterion compliance according to the type of analysis I mentioned, IRV
nations aren't multiparty either (unless 2.5-party rule counts as
"multiparty"). So something is going on that makes top-two better than IRV.
Now, if advanced ranked methods like Condorcet are good enough, then no
problem. All we need is Condorcet and we're done. But if they're not (or
preparing for that possibility), then we should try to figure out why
top-two succeeds where IRV fails - and how we might construct a method
that's both good according to criterion compliance analysis (which is
where the whole LIIA reasoning comes into play) and according to the
counter-Duverger properties seen in top-two.
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