[EM] Holy grail: PAR with FBC?

[Juho Laatu]

Negative votes and default votes that are not bottom votes are often problematic. There can be some problems also with rule "default is accept for voters who do explicitly reject some candidates".

Candidates A and B are considered to be the strongest potential winners. Their first preference support is about 45% and 45%. Candidates from C to Z have much less first preference support.

It makes sense to A supporters to reject B (hoping that rule 2 will eliminate B, even if B would have more support than A). B supporters will do the same to A. It is thus possible (or even probable in this scenario, if the election is competitive) that the leading candidates will be eliminated.

Let's assume that there are no obvious compromise candidates that would be preferred over B by A supporters, and vice versa. Some of the other (than A and B) candidates might be rejected too (those that many enough voters bother to reject sincerely). As a result the winner will be someone that could be quite disliked among both A and B supporters.

A linear opinion space might look like this: D - [C] - [A] - [B] - [E] - F - [G] - ... - X - Y - Z where square brackets point out the eliminated candidates. D and F are maybe the most likely winners, but surprises are possible if many A and B supporters explicitly reject (sincerely but incompletely) only few smaller candidates (e.g. D, C, E, F, G) and thereby give default accept to all the others (e.g. X, Y, Z). If candidate Y has more first preference support than other minor candidates, and some support from X and Z supporters, he/she might win.

If this is of concern, the easiest fix is of course to use reject as default value in all ballots.

BR, Juho


> On 10 Nov 2016, at 17:39, Jameson Quinn <jameson.quinn at gmail.com> wrote:
> 
> 
> 
> 2016-11-10 9:04 GMT-05:00 C.Benham <cbenham at adam.com.au <mailto:cbenham at adam.com.au>>:
>> 1. Voters can Prefer, Accept, or Reject each candidate. Default is Accept.
>  
> This seems to assume that all the voters are interested in all the candidates and like checking boxes, whereas
> I should think that a lot of voters would be only interested in their favourite and content to keep voting the
> way they did under plurality (and would presumably continue to do so under Approval).
> 
> They should be allowed to continue giving the most effective vote possible by simply giving a "Prefer" rating to their
> favourite.  In-effect penalising such voters for forgetting to also give "Rejects"  to all their non-favourites is unfair
> and dumb.
> 
> It will give voters who aren't fans of the new method extra reason to resent it.  Suppose that a strong candidate
> from an established party very narrowly loses just because some of his/her supporters forgot to give out "Rejects".
> Don't you think that might fuel a movement to dump the method?
> 
> My thinking was that in most real-world situations, you'd only have to check one prefer and one reject to get maximum effectiveness, and it would be obvious which to reject.
> 
> But I see your point. So I'm changing the method to: "Default is reject for voters who do not explicitly reject any candidates, or accept for those who do." 
> 
>> 2.Candidates with a majority of Reject, or with under 25% Prefer, are eliminated, unless that would eliminate all candidates.
> 


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