[EM] Manipulability stats for (some) poll methods
Chris Benham
cbenhamau at yahoo.com.au
Sun Apr 28 20:01:38 PDT 2024
CLC,
> Chris—here in the United States, pushover is well-known and frequently
> used, in the context of partisan primaries. We refer to it as "raiding".
That doesn't surprise me in the least. Your crazy party primary system
is a big open red-carpet invitation to pushover strategists. I think
Nikki Hayley was Trump's last opponent in the Republican primaries to
drop out. On YouTube I saw one of her "supporters" interviewed.
He openly stated that he was only participating in that contest to try
to "stop Trump", and no matter who was the Republican nominee he was
definitely intending to vote Democrat in the general election.
In October last year Rob Lamphier asked me about Push-over in Australia:
>/Is "pushover" strategy common in Australian elections, and commonly //named by that name? /
No and no. I've only ever come across the term here, and from that Blake Cretney page.
Seats/districts where that would even be a theoretical possibility would be rare. I did read a report in a newspaper some time in the 1980s that the conservative Liberal Party toyed with the idea of doing that in one seat, but rejected
the idea on the grounds that it would undermine the perceived integrity of the election process and so the legitimacy of the winner. Bear in mind that we have "compulsory voting" which is popular, because it is widely accepted that voting is a civic duty.
In that district the highly predictable FPP order was Right > Centre-Right > Centre-Left, or if you want the parties' names Liberal > Australian Democrats > Labor.
It was also highly predictable that nearly all of the Labor voters would give their second preference to the Democrat and that a big majority of the Democrat voters would give their second preference vote to the Liberal. (Bear in mind that truncation isn't allowed).
In that circumstance the Liberals could have organised for some of their supporters to vote Labor to "rescue" that candidate from being eliminated, so that instead the Democrat will be eliminated and then the Liberal will win in the pairwise contest with Labor. BTW, the Democrat was the sitting member (and it may have been that party's only seat in the state parliament,Labor and Liberal are the two major parties). Of course the Democrat was the Condorcet winner, but no-one even had that concept.
> I suspect Australia doesn't have any examples of turkey-raising
> because it only has two major parties in its IRV seats, at which point
> the strategy is pointless.
That is far from the main reason, and isn't universal. It's obviously
much more difficult than in the US with a primaries system or a Top-Two
Runoff. In that situation once the strategists have achieved their first
objective, getting the "turkey" into the final (or the general election)
they can then vote "honestly" to help defeat that candidate in the final
decisive stage.
But with Hare, the strategists have to stick with their insincere vote
supporting the turkey in the final and just hope that enough other
voters will overwhelm their votes and defeat the turkey. This obviously
makes the risk of backfire (i.e. the turkey winning) much greater.
The strategists have to be careful that there aren't too many of them
(while of course it won't work if there are too few).
One mistake I think that voting reform enthusiasts in the US make is
that they over-estimate the effect of the electoral system/method on the
political culture as well as over-simplifying it.
For example they want more viable political parties and seem to assume
that all two-party dominated systems are roughly equivalent. But the one
with Hare is much better. In the FPP landscape the major parties can
foist unpopular candidates and/or policies onto the voters and say "You
have to vote for us because otherwise you'll just be wasting your vote
and letting your Greater Evil other major party win." But in the Hare
landscape (especially with relatively easy ballot access) their ability
to do that is sharply curtailed.
Because the voters can then just turn around and nominate and support
independent candidates that support the same "side of politics" as their
usual favourite major party, with a chance to defeat the major party
candidates without helping the "wrong" one to win.
So one possible effect of replacing FPP with Hare is just that the two
major parties will both improve their behaviour and sensitivity to
voters to stop that from happening, and the whole system will serve
voters much better but still remain "two-party dominated".
The political culture of Australia assures that any attempts at Pushover
strategy would be kept very quiet, so I suppose I can't guarantee that
it's never been tried or succeeded. But I'd be be surprised.
Chris B.
On 29/04/2024 10:05 am, Closed Limelike Curves wrote:
> Chris—here in the United States, pushover is well-known and frequently
> used, in the context of partisan primaries. We refer to it as "raiding".
> Usually it's difficult to notice, and I suspect the same is true in
> Australia. The only difference is here in the United States we manage
> to notice it from time to time, because what happens is candidates
> will run big advertisement operations that aim to promote an extreme
> candidate in a primary and give an easy win. I can't prove the same
> thing happens with voters, but I'm not sure how you /would /prove that.
>
> I suspect Australia doesn't have any examples of turkey-raising
> because it only has two major parties in its IRV seats, at which point
> the strategy is pointless.
>
> On Sun, Apr 28, 2024 at 4:14 PM Chris Benham <cbenhamau at yahoo.com.au>
> wrote:
>
>> Michael—you're right that it means favorite-burial (cutting the
>> "head" off a ballot). The term is quite old, though (older than
>> "favorite betrayal" or "favorite burial" I believe)
>> <https://www.cambridge.org/core/product/identifier/S0003055400194481/type/journal_article>.
>
> I don't like either term. For me, "burial" refers to something a
> voter does to a candidate in the hope that will cause that
> candidate to lose to a candidate the voter prefers, and not just
> to any insincere down-ranking. So "favorite-burial" is an
> oxymoron that Mike O. likes to use.
>
> "Favorite Betrayal" meaning to insincerely down-rank one's
> favourite, is ok, but that could either be Compromise strategy
> (insincerely up-ranking X to decrease the chance that X will lose
> to a candidate you like less) or Push-over (insincerely up-ranking
> X to increase the chance that X will lose to say F that you like
> better, instead of F losing to some Y that you like less).
>
> An attempt was made to standardise the terminology here quite a
> while ago:
>
> http://condorcet.org/emr/defn.shtml
>
>> *burying*
>> Insincerely ranking an alternative lower in the hope of defeating it.
>> *compromising*
>> Insincerely ranking an alternative higher in the hope of getting
>> it elected.
>> *push-over*
>> The strategy of ranking a weak alternative higher than one's
>> preferred alternative, which may be useful in a method that
>> violatesmonotonicity
>> <https://web.archive.org/web/20090613041320/http://condorcet.org/emr/defn.shtml#monotonicity>
>>
>> *monotonicity*
>> The property of a method where an alternative can never be made
>> to succeed by being ranked lower on some ballots. Doing this is
>> using the "push-over
>> <https://web.archive.org/web/20090613041320/http://condorcet.org/emr/defn.shtml#push-over>"
>> strategy.
>>
>>
>
> The genius of STAR Voting is that it apparently technically
> doesn't "violate monotonicity", but it is vastly more vulnerable
> to Push-over than IRV which does, as I've explained previously.
>
> I find the question of whether there have been mistakes or
> exaggerations or false claims made by the IRV promoters to be
> completely irrelevant to, and a separate question from, whether
> its adoption in the US should be supported.
>
> Of more concern to me are the details of the ballot rules and
> restrictions. I think it is more democratic for it to be
> relatively easy to get on the ballot so as to allow the voters a
> wider choice of candidates. I understand that typically voters are
> limited to 7 different "ranking levels". Well say there are 9
> candidates and my two least-preferred candidates are the two
> front-runners and I have a preference between them. If I vote
> sincerely my vote is just as wasted as if I had voted sincerely in
> FPP.
>
> IRV then doesn't have Clone Independence. One of the main points
> of ranked-ballot versus FPP is to reduce the involuntarily wasted
> vote as much as possible.
>
> If such restrictive ballot rules are unavoidable, then I lose my
> enthusiasm for IRV or Benham in favour of something with a
> truncation incentive (and that is happy with equal-ranking if that
> isn't a problem for the ballot rules) such as Smith//Approval
> (implicit).
>
> Properly implemented Hare's Compromise incentive is practically
> nothing by comparison with that of FPP, and no-one in Australia
> notices it. I estimate it is also quite a bit weaker than that of
> STAR. Pushover strategy in Hare is relatively difficult and risky
> in Hare and as far as I know it's never been tried in Australia.
> Whereas STAR is a "festival of Push-over" farce/nightmare.
>
> And while (like STAR) it fails Condorcet, it has a solid set of
> "representativeness" criterion compliances that together can be
> thought of as weakened Condorcet and are worth quite a lot.
>
> They are Dominant Coalition (a better stronger version of Mutual
> Majority that so of course implies it) and Dominant Mutual Third
> and Condorcet Loser. STAR only meets the last of those, the weakest.
>
> Chris B.
>
>
> On 29/04/2024 5:08 am, Closed Limelike Curves wrote:
>> Michael—you're right that it means favorite-burial (cutting the
>> "head" off a ballot). The term is quite old, though (older than
>> "favorite betrayal" or "favorite burial" I believe)
>> <https://www.cambridge.org/core/product/identifier/S0003055400194481/type/journal_article>.
>>
>> On Sun, Apr 28, 2024 at 12:02 PM Michael Ossipoff
>> <email9648742 at gmail.com> wrote:
>>
>> Of course I’m just guessing, but my guess is that
>> “decapitation” is Closed’s new name for favorite-burial.
>>
>> Closed sometimes in invents new names without define them.
>>
>> IRV indeed shares Plurality’s need for favorite-burial
>> defensive-strategy. I don’t like that, & wouldn’t propose
>> IRV. There are a number of places where IRV is (the only
>> electoral reform) up for enactment this year, In spite of
>> that very unlikeable strategy-need, I wanted to help
>> campaign for its enactment, in the hope that the voters
>> who’ve enacted it didn’t do so because they intend to bury
>> their favorite, & so so won’t do so.
>>
>> But, because IRV is being fraudulently sold to them, with
>> intentional lies, we can’t count on how people will vote when
>> they find out about what they’ve enacted…when they find out
>> about the lie.
>>
>> Therefore, regrettably, we shouldn’t support “RCV”.
>>
>>
>> On Sun, Apr 28, 2024 at 11:15 Chris Benham
>> <cbenhamau at yahoo.com.au> wrote:
>>
>> Limelike,
>>
>> Can you please define and explain the "decapitation"
>> strategy? I haven't heard of it.
>>
>> And can you elaborate a bit on this? :
>>
>>> IRV is a good example of this. It's /usually/ not
>>> susceptible to strategy (in the IAC model), but I think
>>> of it as one of the most strategy-afflicted methods on
>>> this list. It's vulnerable to some
>>> particularly-egregious strategies (decapitation), ones
>>> that are complex or difficult to explain (pushover), and
>>> many strategies [that?] don't have a simple defensive
>>> counterstrategy available (like truncation).
>>
>> Chris B.
>>
>> On 29/04/2024 2:31 am, Closed Limelike Curves wrote:
>>> Hi Kris, thanks for the results! They're definitely
>>> interesting.
>>>
>>> That said, I'm not sure how useful a metric raw
>>> probabilities provide; I don't think they provide a very
>>> strong measure of how /severely/ each system is affected
>>> by strategy. Missing are:
>>> 1. How much do voters have to distort their ballots? Is
>>> it just truncation, compression (as with
>>> tied-at-the-top), or full decapitation?
>>> 2. How hard is it to think of the strategy?
>>> Counterintuitive strategies (e.g. randomized strategies
>>> or pushover) require large, organized parties to educate
>>> their supporters about how to pull it off. This could be
>>> good or bad depending on if you like institutionalized
>>> parties. Good: sometimes people can't pull it off. Bad:
>>> this creates an incentive for strong parties and
>>> partisanship. See the Alaska 2022 Senate race, where
>>> Democrats pulled off a favorite-betrayal in support of
>>> Murkowski to avoid a center-squeeze.
>>> 3. Is a counterstrategy available?
>>> 4. How feasible is the strategy (does it involve many or
>>> few voters)?
>>> 5. How bad would the effects of the strategy be? Borda
>>> is bad not just because it's often susceptible to
>>> strategy, but because it gives turkeys a solid chance of
>>> winning.
>>>
>>> IRV is a good example of this. It's /usually/ not
>>> susceptible to strategy (in the IAC model), but I think
>>> of it as one of the most strategy-afflicted methods on
>>> this list. It's vulnerable to some
>>> particularly-egregious strategies (decapitation), ones
>>> that are complex or difficult to explain (pushover), and
>>> many strategies don't have a simple defensive
>>> counterstrategy available (like truncation).
>>>
>>> A low-probability but occasionally high-impact strategy
>>> might be the worst of both worlds; voters get lulled
>>> into a false sense of security by a few elections where
>>> strategy doesn't matter, then suddenly find a candidate
>>> they dislike elected because they failed to execute the
>>> appropriate defensive strategy.
>>>
>>> ----
>>> Election-Methods mailing list - seehttps://electorama.com/em for list info
>>
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