[EM] Suppose, for a moment, there were never any cycles...

Kevin Venzke stepjak at yahoo.fr
Sun Jan 22 06:08:20 PST 2023

 Hi Robert,

> Well I don't really expect to prevent cycles, but just by doing nothing, I can plan on them
> being extremely rare, 0.2% of the time.  So it's a faux-suppression of cycles, a
> pseudo-effect.  Either way, I can say that the reason that IRV is good at avoiding the
> spoiler effect is solely because 99.4% of the time IRV elects the Condorcet winner.

That sounds to me like a pretty big concession.

To the extent a method deals badly with spoilers, the interested parties will aim to avoid
the issue through their nomination choices or voting advice.

For example FPP always elects the CW on those ballots. Spoiled FPP elections aren't that
common. But we would probably say that's because they tried not to have 3+ candidates on
the ballot, not because FPP is so Condorcet-efficient.

I can't say with any certainty how different the nomination incentives under IRV are in
comparison to any specific Condorcet method, but they shouldn't be the exact same. One
obvious element is that a would-be IRV candidate expecting few first preferences is
probably not viable, and so might choose not to run for that reason. I hope Condorcet
incentives are noticeably different in this sort of vein. Otherwise this statement above
seems to tell me that IRV is 99.4% right already, that all we can do is fix the 0.6%, and
that seems a little demotivating to me.


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