[EM] Range Voting "unbeatable"?

[Jameson Quinn]

2009/8/30 Warren Smith <warren.wds at gmail.com>

> > "utterly false" is a bit strong language
>
> --No: "absolutely" "unbeatable" is what is "strong language."
> And it is false.   And what really pisses me off, is you accusing me of
> being false, when it was you all along being false, and indeed I had
> publicized the exact opposite of what you falsely said and falsely
> attributed to me.    The correct response is
> to apologize (jerk), not to come back accusing me of "strong
> language"! Holy cow!
>

I'm really sorry if I was being unintentionally abrasive, to the point which
would have justified you calling me names. I can honestly say that I have a
lot of respect for you and I hope we can keep any further debate in the
realm of ideas and not name-calling.

I am not accusing you of being false on this point. I am saying that you are
using strong language, extending a good result on RNEM to be generally
applicable when it's not.

Your BRBH system is derived in the case of 3-candidate RNEM. Say I create
another elections model, in which voters have a bimodal utility distribution
for the 3 candidates, with a gap in the middle. Then, a (-1, 0, 1) vote is
Bayesian evidence that the voter is one of the 1/4 who is sampling all three
candidates from the same utility mode, and therefore evidence that the
BRBH-like "denormalization" weighting factor should be at a minimum, not a
maximum. A vote that's more like (-1, 0.9, 1) or (-1, -0.9, 1)is, on the
other hand, evidence for a high "denormalization" factor. So in this voter
model, BRBH is significantly worse than plain Range.

Yes, it is probably false that Range is "absolutely unbeatable" in BR with
100% honest voters. But without specifying the model, it's going a little
too far to say that it's "utterly false". Anyway, I'm sorry we are getting
distracted here. The original point I intended to concur with (and *I'm
sorry* I didn't clarify in my concurrence) was that it is not really worth
trying to beat Range's BR with honest voters, in simply practical (not
mathematical) terms. Can we agree on that?


>
>
> > I completely reject your model of strategic voters. It is simply not true
> that, if you surveyed all voters their honest opinions of who the two
> "frontrunners" are, all of them would agree in 100% of elections.
>
> --Ok, the truth is not 100%, it is "over 98%."
> Indeed, it is possible (proven by test) to predict all important US
> races with >98%
> accuracy over 1 year ahead of time.  Proof:  see remarks on Ron Facheux
> here:
> http://www.rangevoting.org/NonVoters.html
> Also: note the percent of third-party winners in the USA in such races
> is below 1%.
>
> OK.  Now, is this difference between 100 and 99% really a good basis
> for your "complete rejection"?  Golly.  Gee willickers.  Total
> unrealism!  You ARE finicky.


Your own graphs show that, for infinite numbers of voters, any epsilon of
strategic voters causes a discontinuous increase in BR. If you graphed the
"voters can predict frontrunners with x% accuracy" versus number of
strategic voters, it would have a similar discontinuity. With finite numbers
of voters, it would just be nearly discontinous, rising to 100% as the
strategic voters become something like the square root of total voters. If
you found 99% on that graph, and then projected down with that same fraction
of strategic voters to the similar graph for some non-plurality election
system, I think you'd get a number far less than 99%.

In other words, I think the empirical 99% is nearly entirely explained by
the special flaws in plurality, and that, given those flaws, the fact that
it isn't 100% is, if anything, evidence that a two-frontrunner strategy
model will not work for non-plurality systems.


>
>
> >I propose (and you have not responded) a different model of strategy.
> 1) Choose an underlying voter utility model which behaves roughly like
> reality. This is an area for research, and my own incomplete ideas
> don't fit here...
>
> --actually, I already did this, and did it before you came along and
> said this.
> (See a common theme?  'Cause I'm noticing one.)
> IEVS already includes "reality-based utilities" based on a dataset of
> real world elections.
> It turns out, when you run the experiment, that using reality-based
> utilities leads to little-to-no discernible difference in results,
> versus using fantasy-based utilities like
> I had before.
>

Sorry, I didn't acknowledge that you've done the best work I know of in this
realm. I personally think we all owe you a debt in this regard: thank you.
Still, this is only step 1 of my proposed scheme.


>
> >I can make Range behave like "random candidate" by assuming that candidate
> X's voters strategically bullet-vote and all other voters vote honestly.
> (For infinite numbers of voters in RNEM, you just assign a random epsilon(k)
> fraction of bullet voters to each kandidate, and then whichever one has the
> highest epsilon(k) wins.) Both assumptions are unrealistic worst-cases but
> arguably a significant drain factor on the systems' overall quality.
>
> --this seems unlikely to be a realistic model. But if you think it is
> realistic, then fine.
> Put it in IEVS, and compare range to other voting systems under that model.
> In particular, under the very model you just proposed, you will find
> that Condorcet
> systems also elect the highest-k guy.   Congratulations. You just
> proposed a new model and found range and Condorcet and random
> candidate all behaved the same under that model.   Which is fine, but
> seems little basis for "[range] is not as great as you depict it."
> I mean (since you seem to be a Condorcet supporter?) wouldn't it be a basis
> for saying Condorcet is not as great as YOU depict it?
>

OK, a couple of points:

1. I did ask you for a link to the source code of IEVS, please. I'd like to
do this.

2. If you follow the strategy model I gave, it is not obvious that Condorcet
models do this. Even if different ideological groups of voters have
different strategy thresholds, methods which are more resistant to strategy
can either discourage strategy altogether or prevent it from having such an
absolutely decisive impact that the most-strategic group just wins, period.

Jameson
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