[EM] Second order proportional representation.

[Juho Laatu]

Vulnerabilities are often theoretical vulnerabilities in the the sense that if one group of voters could go back in time after they have seen how others voted, and change the way they voted, they would get a result that all the members of this group find better than the original result. Of course it is not possible to go back in time, or to allow only one afterwards identified group to apply a strategy, or not let other voters change the way they vote, and it is difficult to make each member of the identified group to change his vote in the way that the strategy requires.

I agree that plain lists of vulnerabilities of different methods to different theoretical vulnerabilities is not the best possible approach to estimate the quality of different methods in practical elections. Theoretical analysis and exact knowledge of different theoretical vulnerabilities is needed too, but if one wants to know which election methods would be best in different real life environments, it makes more sense to analyse which vulnerabilities might pose threats in such typical practical environments (when used by regular voters).

One approach to studying this kind of practical vulnerabilities is to try to formulate different vulnerabilities as guidance for practical elections ("if condition A then modify your vote (or votes of all similar minded voters) in way B"). That guidance could be intended for individual voters or for leaders that can study the situation and then give strategic guidance to similar minded voters. I have seen many sensible formulations e.g. on how regular voters should vote in Approval (in practical elections). But as already noted, none for Condorcet methods. This means that it is at least quite difficult to find such working practical strategies for real life Condorcet elections. If there are none, then it may be the best strategy to vote sincerely, which would be good news for practical Condorcet elections.

As I already noted, some basic assumptions for practical elections are that there is no complete information on the opinions of other voters and their planned strategies. One can not (in most cases) fully control how all the voters of some particular interest group will vote. And one must give some space also to possible counter strategies (or loss of support of some candidates because of their strategic plots), when other parties / voters learn that some others are planning to vote strategically. I'm still waiting for the first such practical rule for Condorcet methods. I think there are some situations where practical strategies could work, but such strategies tend to work only in some special situations or under some special assumptions (well known preferences, limited number of candidates, strict party discipline etc.). I'm not aware of any simple practical strategic voting rule that could be applied in all Condorcet elections or with only vague information of the preferences of the voters.

Maybe the question is, what if we would have Condorcet presidential elections in country x next month, do you have some strategic voting recommendation available to all or one of the parties or their members? You may assume availability of some rough poll information now (before you give the recommendation). Or even better if the recommendation is so generic that the voters can make their strategic voting decision based on the last (inaccurate, maybe multiple differing) polls that will be published few days before the election.

Juho


> On 18 Sep 2016, at 23:54, VoteFair <ElectionMethods at VoteFair.org> wrote:
> 
> On 9/16/2016 2:47 AM, Juho Laatu wrote:
> 
> > So, where are the practical guidebooks if Condorcet methods
> > are so vulnerable to all he strategies?
> 
> Good point!
> 
> I could be wrong, but it seems to me that when someone points out a vulnerability in a Condorcet method, it's an edge case.  And edge cases seldom happen in real elections where there are more than a few dozen independently acting voters.
> 
> I tend to think of election-method vulnerabilities in terms of how often a specific vulnerability can/could occur -- rather than yes/no checklists of whether a vulnerability is possible.
> 
> If this concept were converted into visual maps of where the edge cases and vulnerabilities are, the difference between unfair methods (plurality) and medium-quality methods and the best/fairest methods would stand out clearly.
> 
> Richard Fobes
> 
> 
> On 9/16/2016 2:47 AM, Juho Laatu wrote:
>> Few random observations follow.
>> 
>> - Rankings may be too simplifying when forming a cabinet. I think it is typical that some grouping agrees on a program, and then one forms a (majority, multiparty) government/cabinet based on what was the best identified program and majority supporting that program in the parliament. A mechanistic ranking based approach to form the cabinet might be a too straight forward approach for this. Or maybe the idea was to form totally new kind of cabinets (whose structure could not be negotiated by politicians).
>> 
>> - But instead of electing directly the cabinet members, one could use ranked methods also to elect the best government coalition. The candidates could be e.g. A-B-C, A-B and B-C-D, where A, B, C and D are different parties.
>> 
>> - Also not using ranked methods might lead to ranking method style strategic voting. I mean that if the alternatives are A, B and C, and there is a ABCA preference loop, then it may be up to the chairman which alternative will win. If chairman's own party prefers alternative A, then it would make sense to first decide (using plurality) whether B or C is favoured. B wins. And then B will lose to A in the final plurality voting.
>> 
>> - I tend to think that Condorcet strategies are quite difficult to apply successfully even in environments where the opinions of all the voters are quite well known, and when there is a strong party discipline that can be used to force MPs to vote in some particular way (either against their own will, or to strategically support their own targets). There are strategical vulnerabilities (always, for sure), but I still have not seen any good article on how voters (individual voters alone, or party leaders with the help of party discipline) could successfully apply strategies in Condorcet elections. I'm waiting for someone to write it, or otherwise give general guidance on how the system can be cheated (without too much risk of bad results). The fact that sometimes it is possible to see afterwards that some strategy would have worked is not enough (assuming 100% information on how everyone will vote, and still with ability to change afterwards the votes of oneself and other m
> emb
>>  ers of one's own party). I'm assuming that there is no 100% accurate information on the preferences of other voters / parties, and there is no 100% accurate information on what strategies each party is planning to apply. So, where are the practical guidebooks if Condorcet methods are so vulnerable to all he strategies?
>> 
>> Juho
>> 
>> 
>> 
>>> On 16 Sep 2016, at 09:52, Kristofer Munsterhjelm<km_elmet at t-online.de>  wrote:
>>> 
>>> On 09/16/2016 05:52 AM, VoteFair wrote:
>>>> On 9/14/2016 1:06 PM, Kristofer Munsterhjelm wrote:
>>>>> I just read about an interesting idea in this vein by Brams. First you
>>>>> pick your legislature (using whatever method), then once a majority of
>>>>> the parties decide to form a government, the parties sequentially claim
>>>>> ministries according to an order given by a divisor method.
>>>> 
>>>> Here is yet another approach:
>>>> 
>>>> http://www.negotiationtool.com/cabinetministers.html
>>>> 
>>>> The MPs (members of parliament) rank their preferences for possible
>>>> cabinet members, and then a variation of VoteFair ranking calculations
>>>> fills the cabinet positions.
>>>> 
>>>> It mostly uses the algorithms explained at VoteFair.org
>>>> (http://www.votefair.org/calculation_details.html).  Of course a few
>>>> modifications are needed.
>>>> 
>>>> Have questions?  Please ask.  But be patient because I'm writing a
>>>> time-sensitive election article that I will announce later.
>>> 
>>> I've always had the impression that ranked voting isn't going to work in
>>> parliamentary settings because the MPs will feel obligated to strategize
>>> maximally to get what they want, and there are few enough of them that
>>> it is possible to do so.
>>> 
>>> In a system with strong party discipline, the party leaders or whips
>>> could very well order their respective MPs to vote in a particular way.
>>> 
>>> Am I wrong when making that assumption?
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