[EM] Real IRV Election, Disputable Result

Jonathan Lundell jlundell at pobox.com
Sun Mar 12 12:24:01 PST 2006

At 1:57 AM -0700 3/11/06, Jan Kok wrote:
>I crunched the election data and found that Kiss was preferred to
>Miller, 4755 to 3988.
>Drat. :-)

That's still not numerically consistent with the published Burlington 
results; I wonder what the discrepancy is.

Let me dispute your "drat", though. Your thrust, I suppose, is that 
you'd like to find an IRV election in which there was a Condorcet 
winner not elected by IRV. I suggest that this quest is based on a 
fallacy, and that such a result could not legitimately be used to 
argue the merits of IRV vs Condorcet ranking.

I'm not arguing the merits of IRV vs Condorcet here; I go back and 
forth on the question myself. I'm only arguing against the validity 
of a particular sort of evidence.

The fallacy lies in different voter behavior. IRV and Condorcet 
ranking come with different guarantees to the voter. An example (and 
there are examples on both sides) is that IRV guarantees 
later-no-harm. That is, the IRV voter can freely rank lower choices 
with the assurance that those choices cannot harm the chances of the 
voter's earlier preferences.

Condorcet ranking does not (and cannot) make that guarantee. So the 
same set of voters (in Burlington VT, say) faced with the same 
candidates but a Condorcet rather than an IRV election, are likely to 
cast different ballots. So to take an election profile that was made 
under IRV rules and apply Condorcet ranking to it might be of casual 
interest, but it's an apples and oranges comparison.

I'm not claiming that later-no-harm is a decisive argument in favor 
of IRV; Condorcet ranking has its own advantages, and later-no-harm 
is not IRV's only advantage. I'm only arguing that you mustn't change 
the counting rules after the election without also giving the voters 
a chance to change their ballots in view of the alternate rules.

All this is further complicated, of course, by the fact that voters 
are human, and are neither perfectly informed nor perfectly rational. 
But they're somewhat informed, and somewhat rational, and we must 
expect that the specific election rules in place will have some 
effect on voter behavior.
/Jonathan Lundell.

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