[EM] Manipulability stats for (some) poll methods

[Michael Ossipoff]

Sure, Above-Mean is one of the main 0-info strategies. But so is
Above-Largest-Gap, which, in a simulation, could stand-in for u/a &
Like/Not-Like.

IRV is the prime embarrassment for the maipulability standard.

Yes, the goal of ranked methods is to avoid defensive-strategy need. IRV
has no offensive-strategy (to speak of), & is relatively unmanipulable, but
it has a really big need for drastic defensive-strategy, favorite-burial.

So I’m just saying that it would be better to report about the latter
instead.

We all agree that avoidance or reduction of defensive strategy need is the
goal of rank-methods. So, report that instead of
“manipulability”.

Comments inline:

On Wed, May 15, 2024 at 11:23 Kristofer Munsterhjelm <km_elmet at t-online.de>
wrote:

> On 2024-05-15 10:46, Michael Ossipoff wrote:
> >
> >
> > On Tue, May 14, 2024 at 08:58 Kristofer Munsterhjelm
> > <km_elmet at t-online.de <mailto:km_elmet at t-online.de>> wrote:
> >
> >
> >>
> >
> >
>
> It tells you how often you have to be thinking about "playing the
> strategy game" to improve the outcome (or how often you may regret if
> you don't).


It doesn’t!!

IRV makes you play the strategy-game, & will make you regret that you
didn’t bury your favorite.



In a low manipulability method, you don't have to start
> thinking about whether you should tailor your response to poll data,
> etc. as much.


No, not poll-data, but the method’s own intrinsic wrongdoing.


>
> There are two approaches here: you can make an apparently simple but
> highly manipulable method and then place the burden of voting "the right
> way" on the voters. Or you can take the spirit of the revelation
> principle further (it can never go all the way) and place that
> responsibility on the voting method itself.


Yes, & that’s another issue. I’ll comment about it below where you bring it
up.

>

IMHO, the more a voting method supports "just go there and submit your
> vote", the better it is, all else equal. As I have pointed out, it's not
> the full picture - you also need to know that the sincere unmanipulable
> outcome isn't going to suck. But that doesn't mean manipulability is
> meaningless.


It means that it would be better to just speak of & measure for what is
desired. No need to measure, report & speak of a fragment-component that
isn’t helpful by itself. Skip that & just report directly regarding the
desideratum itself.

Yes, many want the method to do everything for us. In fact I agree with RBJ
that, for an inimical electorate (like our public political elections), the
completely legalistic pairwise-count rank-methods (Condorcet) would be
best…all else being equal, as you said.

But all else is *not* equal !

Count-fraud is a problem. Condorcet’s humungously computation-intensive
count ridiculously facilitates count-fraud.

You want to do a handcount-audit of a Condorcet count?

Additionally, the count-program itself is easier to hide or add fraud-code
in.

As a general principle, then yes it’s much better to have the voters do it
for themselves rather than having a complicated fraud-prone
automatic-machine do everything for them.

A simple, reliable hand-tool is much better.

I’d much rather trust the voters to use the simple reliable hand-tool
(Approval) well, than trust everyone responsible for the count to not
perpetuate count-fraud.

I’m glad you brought up the desire for the method to do it all for
us…taking our sincere rankings as input, & outputting the legalistic right
choice. …because I’ve been meaning to address that matter.

…& that’s not even counting the much less expensive implementation (could
be zero cost, without even new count-software), easier less expensive
administration, & easier simpler explanation with consequent easier
enactment.

Approval isn’t as difficult to vote as it opponents claim.  There are many
ways to choose what or whom to approve. That’s a good thing, because you
can choose how you like.

Condorcet is legalistic, but we don’t have to be legalistic! Approval
guarantees election of the candidate who maximizes the number of voters for
whom the outcome is in their preferred of the two merit-subsets, however
the voter designates them.

e.g. If people approve what they like, Approval maximizes the number of
people who like the outcome.

If people approve what’s acceptable, then Approval maximizes the number of
people for whom the outcome is acceptable.

If people approve above expectation, then Approval maximizes the number of
people for whom the outcome is above expectation…maximizes the number of
people pleasantly surprised.

You don’t know the objectively-optimal vote? Neither does anyone else, so
don’t worry about it!

Probability, & therefore expectation & it’s optimization, depends on your
information.

Approving above your subjective perception of expectation genuinely
maximizes your expectation.

Ways of maximizing your expectation:

Approve everyone you’d appoint instead of holding the election. Or approve
everyone whose election wouldn’t disappoint you.

The polling CW is a good estimate of election-expectation. Approve hir &
everyone better.

If you perceive 2 likely frontrunners, approve the better one & everyone
better. (…but don’t believe the bullshit that the Democrat & the Republican
are the 2 choices).

If all were acceptable, I’d just approve whom I like. If I like them all,
I’d approve above mean, if I perceived the mean. But do we perceive the
mean? If not, maybe I’d approve the best half of them, or above the biggest
merit-gap.

Those are my comments. None farther down. Easier to say that than to delete
the rest of the text m.







>
> >>     That Approval and Score are on the high end makes sense to me
> because
> >>     strategy (watching the polls) is such an integral part of the
> greater
> >>     dynamic. Anybody who looks at the polls and then focuses his cutoff
> to
> >>     maximize the effect will have a good chance of changing the outcome,
> >>     and
> >>     reducing a fully ranked non-dichotomous ballot down to an
> >>     approval-style
> >>     ballot to begin with is somewhat of an art.
> >
> >
> > If “manipulation” consists of getting, by voting insincerely, an outcome
> > better than what a sincere ballot would get, then what do you mean by a
> > sincere ballot in Approval?
>
> For a near-dichotomous opinion (A > B > C >>>>>> D > E > F), the answer
> is easy. But for fully general opinions, you're absolutely right. You
> have to make some assumption on honest behavior.
>
> But it seems like the ambiguity is fundamental to Approval. The strategy
> tester works by generating ballots for a sincere first stage and then
> seeing if coalitions can change the winner. The defining feature of the
> sincere stage is that nobody takes information about anybody else into
> account (and that it adheres to the model, e.g. spatially distributed
> utilities, impartial culture, whatnot).
>
> So we need some way for the virtual zero info voters to transform
> utilities to Approval ballots. The virtual voters have to answer Robert
> Bristow-Johnson's question: "do I approve of my second favorite"? And
> it's not at all clear how they should do it.
>
> This reflects a property of Approval itself. The Approval ballot asks an
> ambiguous question and it's up to the voter to interpret it.
>
> Note that this ambiguity doesn't misclassify sincere ballots as
> insincere ones. In the second (strategic) stage, any voter is allowed to
> submit any ballot so long as it'll serve their purposes. What it does
> affect is the weighting (how often would this particular first-stage
> Approval election happen).
>
> In practice, what the simulations do is use some kind of translation
> function. Both JGA and I use a mean utility cutoff. It would of course
> be possible to vary the "translation function" to see if the results are
> robust.
>
> > Above-Mean is one strategy that you can use. It’s one among many. …&
> > it’s incorrect to say that any other way of voting is insincere. As I
> > said, any strategy not obviously suboptimal is weakly-sincere.
>
> It doesn't say that any other way of voting is insincere. It would just
> consider the other ways of voting to happen too rarely or too often
> given the spatial model.
>
> Ultimately, we need a reasonable model of how sincere voters would vote
> in the absence of poll data. Just like we need a reasonable utility
> model to begin with (spatial vs IIA vs whatever). If the model is
> unreasonable, then the results will be wrong. (Just like a wrong utility
> model would produce wrong VSE or ranked method manipulability values.)
>
> If it's impossible to create such a reasonable model because Approval
> voting in non-u/a settings is too intervowen with the wider "adapt to
> the polls" strategy, then there will be no meaningful results. But then,
> that would be telling in itself.
>
> >>     Someone on reddit said: "I would never vote in an Approval election
> >>     without reviewing all the polls…
> >
> >
>
> > Voting for the Acceptables, or ( if everyone is acceptable), for
> > everyone you like, or ( if you like or dislike them all), for those
> > above the biggest merit-gap, or above the mean, lor (if you don’t have
> > an estimate for the mean),voting for the best half of the candidates…
> > etc.:  Those ways of choosing how to vote don’t need polls.
>
> Would running the simulations with different transformation functions
> corresponding to the approaches you listed help, or would you still
> consider the values to be meaningless?
>
> > About Beatpath, MinMax & Ranked-Pairs: Did you use wv or margins?
> >
> > In roughly 1/3 of the elections, those methods were reported as having
> > someone gain from insincerity. That’s surprising if wv was used.
>
> I used full ranking, so wv vs margins makes no difference - though my
> code is set to use wv.
>
> >>     but wouldn't care in a Baldwin's
> >>     election. It's not really about the raw complexity of the strategies
> >>     itself, but their relevance."
> >
> >>     So what I would take from the manipulability values is that we
> should
> >>     try to find a method that both has good honest outcomes, and is
> >>     resistant to strategy away from those honest outcomes. IRV fails the
> >>     former; the cardinal methods fail the latter.
> >
> >
> > …because manipulability, by itself doesn’t measure strategic merit.
>
> That's not quite what I'm saying. Consider Random Ballot. It has zero
> strategic merit because strategy will never help you: if you're the
> fortunate voter whose first preference was picked, you can't do better
> than getting your honest first preference. And if you're not that
> fortunate voter, nothing you can do will make a difference.
>
> So the strategy potential is zero, as would its manipulability be (with
> "who is the lucky voter" held fixed between the honest and the strategic
> round).
>
> But its honest outcome, even in expectation, is really awful. If you add
> a variance penalty, it gets worse still. Nobody proposes Random Ballot
> as a single-winner method.
>
> Manipulability rightly measures its strategic potential to be zero. But
> we need more information: how good its honest outcome is. Same here.
> That doesn't mean that manipulability is a useless strategy measure. It
> just means it doesn't answer the other question we're interested in.
>
> -km
>
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