Post by Jameson QuinnI think the following article contains much that's worth discussing on
these lists
https://democracychronicles.org/12-best-voting-systems/
I'm going to have my own comments on this, but I'll send this out first
to give people a chance to read it for themselves.
What the article says isn't all that surprising, given what Mike has
written on EM itself.
Let's take the Approval CD analysis first. If you assume that:
- There are three candidates of importance
- There's an U/A setting
- Strategy is being coordinated by large party factions
- These large party factions strategize maximally,
then the conclusion follows (except for the bit "the best available
information", as if the parties maximally strategize, then the polls may
also be suspect).
But this isn't what concerns me about Approval. What concerns me about
it is a semi-strategic/semi-honest situation where the C (Nader) voters
"really" have a C>B>A (Nader>Gore>Bush) preference. Now the honest
voters have to do all the cognitive burden of finding out whether to
approve CB or only C, and if they get it wrong, they're not going to
like Approval.
See Forest's remark on Approval "externalizing" strategy at
http://lists.electorama.com/pipermail/election-methods-electorama.com/2016-October/000717.html
and my post about manual DSV at
http://lists.electorama.com/pipermail/election-methods-electorama.com/2016-October/000715.html.
Mike might respond that the same problem exists with ranked voting and
so the argument above doesn't save e.g. MAM. But a honest voter knows
how to vote in MAM: C>B>A. If the honest voter values his integrity more
than he does getting his favorite, then ranked methods let him vote
unambiguously. If there are no honest voters, then I agree that the
problem also exists here, but that's a pretty big if.
Apart from that, I can see the use of CD-resistant ranked voting methods
in situations where there's a lot of offensive strategy. In my
experiments with a certain class of Condorcet methods, there seems to be
basically two types of method as far as strategy resistance goes:
- Reversal symmetric, monotone methods where ~70% of IIC 3-candidate
ballot sets are susceptible to strategy at best,
- other ones at about 10% at best,
and methods that pass the CD criterion (or suitable generalizations of
it for voting methods where only strict full ranking is permitted) tend
to be in the second category. I use words like "tend to" because I
should really check this more carefully.
What are MAWP and MAWP2? I haven't heard those abbreviations before.
It'd also have been nice to have seen some mention of how well these
methods resist strategy on the party end, such as cloning. But again, my
impression is that I'm more concerned with cloning and Mike is more
concerned with voter-induced strategy.
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