[EM] [ApprovalVoting] Re: The IRV-Disease has reached my town.

Tue Mar 5 10:01:27 PST 2019

> On 05 Mar 2019, at 16:04, Chris Benham cbenhamau at yahoo.com.au [ApprovalVoting] <ApprovalVoting at yahoogroups.com> wrote:

>> Also here you assume that there is an implicit approval cutoff after the ranked candidates. What if the votes are sincere and there is no implicit approval cutoff?
>> 
> No, I'm only "assuming" that positional information is more meaningful than which candidate is "closer" to being the Condorcet winner
> according to Margins or which candidate needs the fewest additional bullet-votes to become the CW.

If the added implicit information is not approval of all the ranked candidates, does the "positional information" maybe refer to some Borda like rating information? (or maybe implicit ratings) (I don't really like Borda ratings as additional information either because of the associated nomination related problems.)

> 
> Given that Margins is very vulnerable to Burial strategy the argument that it's worth putting up with that because with sincere votes B
> in this scenario is the best (or a good or even acceptable) candidate is .. what??
> 
> Or to put it another way, assuming the votes are sincere, you arguments against electing A or C are what?

I just thought that B might be ok if we take the votes to be plain rankings (= pairwise preferences) with no additional approval or positional information assumed. The mentioned votes are of course very extreme (only three kind if voters), so they are not a typical set of votes form a real life election.

46 A
44 B>C
10 C

One could think that A is a left wing candidate, C is moderate right, and B is far right (because there are 44 voters that rank them in such linear order). A voters don't seem to care which one of the right wing candidates wins (they are tied in every single vote). The B voters have a clear and understandable position, with full rankings. The C voters have not ranked B. Maybe they are so centrist that A and B are equally good to them.

Condorcet methods can be said to elect a compromise candidate that is not too bad for anyone (sometimes the Condorcet winner might have no first preference votes). I therefore try to find an explanation to why B might win, from this point of view (= elect he best compromise (that is not very disliked)).

Since the A voters did not rank C above B, we must assume that they are perfectly ok with electing B, if A does not win. Same with C voters. B voters have a clear preference C>A (if B can not win).

If A wins, B and C supporters (54, majority) clearly think that C would have been a better choice (and 44 voters would prefer B). If C wins, 46 voters would prefer A, and 44 voters would prefer B. If B wins, 46 voters would prefer A, and 10 voters would prefer C. B doesn't look too bad in this comparison. B might be a better compromise than A or C. I.e. less complaints and rebellions after the election.

(I tried to avoid the "few votes short of being a Condorcet winner" argument since you might not appreciate it.)

> 
>> One might face problems sooner with sincere voting than with strategic voting.
>> 
>> First preferences could be as follows.
>> 
>> 30: far-left
>> 21: left
>> 19: right
>> 30: far-right
>> 
>> If we assume that left hates right, and right hates left, the natural approval limit would be between the left wing and right wing parties. We would get mostly votes that rank only left wing or only right wing candidates. And the winner would be with good probability the far-left candidate, not the expected Condorcet winner (left).
> 
> That doesn't bother me much because (a) far-left may be higher "Social Utility" than left

I don't know what "Social Utility" means here. I guess any of the candidates could have that. It might not show up in rankings nor in approvals.

> and (b) probably enough right voters would 
> be aware that the result is unlikely to be decided by Approval and so they would not be taking a huge risk by sincerely ranking left
> over far-left.

I guess this depends on the method. I can't tell if all "ranking + implicit approval" methods would behave well in this respect. I also don't like very much the idea of voters having to cast strategic votes instead of sincere votes (i.e. implicit approvals in the ballots would not mean that the voter would approve the candidate, but something strategic instead).

> 
> But having said that, Smith//Approval using ballots thatï¿½ allow voters to rank among candidates they don't approve would not be 
> in my book too bad (and much better than Margins).
> 
>> P.S. I think the STV-BTR method that Robert proposed could make a lot of sense in societies where IRV way of thinking is strong.
> That method doesn't have good criterion compliances. It's just a gimmick to smuggle Condorcet compliance past IRV enthusiasts.
> The alternative of just checking for a CW (among remaining candidates) before each elimination is much better.

I'm not a big believer in criterion compliance in real life election methods. In theoretical studies different criteria are excellent measurement tools, but in real life elections nobody cares if the method performs well in some theoretical situations. Often slightly modified (heuristic style, not necessarily "mathematically clean") methods are close enough to meeting those criteria on practice anyway. Also my theoretically ideal "maximally strategy resistant method" might be one that fails to meet most of the named criteria, but does so intentionally in order to violate each one (or many) of them just a little bit, so that it can maximise resistance against all kind of strategies (and keep its worst vulnerability least bad).

> 
>> P.P.S. Limiting the number of ranking levels or number of ranked candidates could make sense when the number of candidates is very high, or just to keep things simple for the vote counting process, or to keep things simple enough for the voters (not to frighten them with the idea of ranking all 100 candidates). I.e. not theoretically ideal, but in practical situations ranking some candidates may be much better than ranking only one, or not bothering to vote at all.
> 
> Limiting the number of candidates the voter is allowed to rank makes no sense. What has happened to your concern
> about "removing information" on who the sincere/ "expected" CW is?

Typically the intention is not to limit the number of candidates that can be ranked (when compared to the situation before he change) but to make that number higher, while allowing it not to be very high. I am still worried about removing information, but I can accept some limitations sometimes (when full ranking is not feasible, or when most voters would not rank all candidates anyway, or when other solutions are not politically possible). The limits should be such that they probably do not lead to not electing the sincere Condorcet winner (or the best candidate when there is no Condorcet winner).

It is for example possible that there is an election with 5 serious candidates (based on some good polling information) and 50 other candidates with no chances to win. In that situation it would not be a big problem to limit the number of ranked candidates to say 7. The ballots could be simpler that way, and voting would not be too tedious. I would not mind someone starting even from 3, if that is an improvement e.g. to the earlier FPTP.

> 
> There would be nothing "frightening" about ranking all the candidates if doing so is purely optional. But voters who wish
> to vote a full ranking should be allowed to. 

That is possible, and a positive thing to do, but I do understand that sometimes also less perfect methods can be "perfect" or "sufficient" for the current real life situation.

Juho

> 
> Chrisï¿½ Benham
> 
> 
> On 5/03/2019 6:42 pm, Juho Laatu wrote:
>>> On 05 Mar 2019, at 07:45, Chris Benham cbenhamau at yahoo.com.au <mailto:cbenhamau at yahoo.com.au> [ApprovalVoting] <ApprovalVoting at yahoogroups.com <mailto:ApprovalVoting at yahoogroups.com>> wrote:
>> 
>>> Robert,
>>> 
>> 
>>> 
>>>> in a ranked ballot, what defines an "approved" candidate?ï¿½ all unranked candidates are tied for last place on a ballot.ï¿½ is any candidate that is ranked at all "approved"?
>>> Yes.
>>> 
>>>> that would change and complicate the meaning of the ranked ballot.
>>> 
>>> Arguably "change" somewhat but I don't see how (overly) "complicate". Allowing voters to rank among unapproved
>>> candidates makes the method more vulnerable to strategy and a lot more complicated.
>> One might face problems sooner with sincere voting than with strategic voting.
>> 
>> First preferences could be as follows.
>> 
>> 30: far-left
>> 21: left
>> 19: right
>> 30: far-right
>> 
>> If we assume that left hates right, and right hates left, the natural approval limit would be between the left wing and right wing parties. We would get mostly votes that rank only left wing or only right wing candidates. And the winner would be with good probability the far-left candidate, not the expected Condorcet winner (left).
>> 
>> The problem with "implicit approval cutoff after the ranked candidates" is that voters would be encouraged not to rank all the major candidates. Not good for Condorcet. That would remove some important information. In this example the sincere Condorcet winner could not be identified anymore.
>> 
>>> 46 A
>>> 44 B>C
>>> 10 C
>>> A>B 46-44 (margin=2)ï¿½ï¿½ï¿½ï¿½ B>C 44-10 (margin=34)ï¿½ï¿½ C>A 54-46 (margin=8)
>>> 
>>> Now Margins elects B,ï¿½ rewarding the outrageous Burial strategy.
>>> 
>>> I can't tolerate any method that elects B in this scenario. Even assuming that all the votes are sincere,
>>> B is clearly the weakest candidate (the least "approved" and positionally dominated and pairwise-beaten
>>> by A.)
>> Also here you assume that there is an implicit approval cutoff after the ranked candidates. What if the votes are sincere and there is no implicit approval cutoff?
>> 
>> Juho
>> 
>> 
>> P.S. I think the STV-BTR method that Robert proposed could make a lot of sense in societies where IRV way of thinking is strong.
>> 
>> P.P.S. Limiting the number of ranking levels or number of ranked candidates could make sense when the number of candidates is very high, or just to keep things simple for the vote counting process, or to keep things simple enough for the voters (not to frighten them with the idea of ranking all 100 candidates). I.e. not theoretically ideal, but in practical situations ranking some candidates may be much better than ranking only one, or not bothering to vote at all.
>> 
>> 
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> Posted by: Chris Benham <cbenhamau at yahoo.com.au>
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