[EM] Manipulability stats for (some) poll methods

Sun Apr 28 17:15:52 PDT 2024

…&, as I likewise said, I wouldn’t have been willing to accept IRV’s
problems if it weren’t for the fact that it’s the only voting-system reform
that will be up for vote this year in several jurisdictions.

On Sun, Apr 28, 2024 at 17:08 Michael Ossipoff <email9648742 at gmail.com>
wrote:

> Chris is right: Primarily it of course isn’t an honesty issue. No matter
> how it’s presented, a method with IRV’s strategy problem should never be
> proposed for public political elections.
>
> …& that’s only the strategy problem, quite aside from its potential for
> count-fraud, due to the elaborate count that it shares with other ranked
> methods. …a problem made considerably worse if the count is automated, as
> it would be here.
>
> There’s no reason to propose something that bad when there are better
> methods.
>
> But I was willing to accept that serious favorite-burial need, &
> count-fraud vulnerability, for no other reason than a hope that maybe most
> voters wouldn’t favorite-bury (as I said in my previous reply).
>
> But that depends on the voters knowing, accepting & liking what they’re
> buying. Fraudulent sale? All bets are off.
>
> On Sun, Apr 28, 2024 at 16:14 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 violates monotonicity
>> <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 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 - see https://electorama.com/em for list info
>>>>
>>>>
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