[EM] Challenge2 - give an example where MFBC is violated for Condorcet methods

[Juho Laatu]

On 9.6.2011, at 8.45, Peter Zbornik wrote:

> Juho,
> 
> I think the coming paper in votingmatters on hybrid methods, shows
> that strategy voting can be a problem in Condorcet methods (beatpath).
> 
> I would say that "fears" in a sense always are irrational, as they are
> emotions. I think, that fears  increase the chance of survival in many
> cases though :o)

I was trying to draw a line between strategies that can be effectively implemented in practical elections and strategies that exist in theory but usually can not be effectively implemented. It is quite easy to check after the election if there was an opportunity for certain group of voters to improve the results from their point of view by casting some strategic votes, but it is much more difficult to see such possibilities and implement them successfully and without too many risks based on the approximate information and changing opinions, changing and uncertain voting behaviour (of allies and enemies) and possible counter reactions before the election. I define irrational strategy as a strategy that will be implemented although the strategic voters have no guarantees that it is likely to cause more benefits than harm to the strategists.

> 
> If there is no apparent "Pol Pot" among the candidates (i.e. the
> extremist, which I would rather see not elecred than having my
> candidate elected), and especially if someone has managed to dumb the
> voters to vote sincerely, then bullet voting is an excellent strategy
> to increase the chances of having your most preferred candidate
> elected as you bury all your competitors.

Are you saying that bullet voting would be a rational (and generally recommendable) strategy (instead of sincere voting) in situations where there are no "Pol Pots"? (rational = likely to cause more good than bad in some practical election)

I tend to think that situations where bullet voting brings benefits are quite rare and hard to identify. Examples where bullet voting harms the voter are on the other hand quite easy to generate.

Term burial should maybe not be used if one does not reverse the preference order of some candidates.

> LNH will not decrease the
> chance of my candidate winning and FBC neither, as all the other
> candidates are equally ranked below the null candidate ("none of the
> above"). I would say, that bullet woting increases the weight of my
> vote compared to a sincere vote, i.e. the bullet voter gets a
> competitive advantage.
> 
> It would be nice to see a study on this topic.
> 
> I would say that bulletvoting is a rational strategy, if you have
> limited information on how others are going to vote, but know they
> will vote sincerely and if you want to get your candidate eleced.

Ok, you seem to be saying that bullet voting is a rational strategy if others vote sincerely. Maybe some additional "limited information" needed?? What would be sufficient additional information?

Or maybe you use term "rational strategy" in the sense that in *some* practical situations that strategy *may* bring benefits. Or, in *some* situations that strategy *would have brought* benefits.

> 
> If the bulletvoting strategy is to be called irrational, then it might
> be good to show the irrationality of the strategy.

I was wondering if it would be irrational in almost all typical political elections / situations (with only limited and unreliable information available). If this holds, then voters could forget that strategy as their own tool and as a possible threat from their competitors.

It is quite easy to find single examples where bullet voting does not make sense. It is also possible to find single examples where it would make sense (at least with perfect information). It is not easy to prove that it would always be in the best interest of all voters in all practical and typical political elections not to use bullet voting. One may try to provide such general guidance that the regular voters could use for their benefit in typical practical elections (in one particular or some set of methods) to demonstrate that some strategy can be implemented efficiently and successfully. That would demonstrate the feasibility of a strategy in practical elections. (Maybe one would have to wait for the first successful implementation of the strategy to be sure.)

> Otherwise, the
> claim that a strategy is irrational might be irrational itself.
> Alternatively, labelling a strategy irrational might be a rational
> strategy to increase the prevalence of certain  strategies like
> sincere voting that might be less efficient in electing the preferred
> candidate than the strategy labeled irrational.
> 
> I think, that by creating an ethical rule, which says, "be honest" and
> by labelling other rules "irrational", those bold enough to ignore the
> rule might be given an advantage in the elections.

Yes, one could distribute also false information on strategies. Here my aim was to ask if some strategies are irrational with high probability so typically that voters could as well forget their existence and just vote sincerely without any worries instead. I guess i also assumed that voters would wake up if something special around these strategies starts happening some day (i.e. they can forget the topic and expect others to warn them if something special happens some day around this topic).

Maybe a better (more neutral and descriptive) term (instead of "typically irrational") to describe this kind of strategies could be e.g. "no need to consider" or "no need to worry" (at least not until further notice by the experts).

Juho


> 
> Best regards
> Peter Zbornik
> 
> On 6/8/11, Juho Laatu <juho4880 at yahoo.co.uk> wrote:
>> On 7.6.2011, at 10.53, Peter Zbornik wrote:
>> 
>>> I'd say that FBC (and LNH) is quite a big problem for Condorcet
>>> methods, at least for someone (like me) who think sincere voting
>>> should be the norm.
>> 
>> One could also claim that in typical political elections Condorcet methods
>> will work fine, and people need not worry about the fact that these methods
>> fail FBC and LNH. FBC does not mean that there would be a clear need to
>> consider "betraying" one's favourite candidate, and LNH does not mean that
>> there would be a clear need to consider truncating one's vote in order not
>> to harm oneself. A much better advice to the voters is to vote sincerely.
>> (And I note again that I have not seen good general advices on how people
>> could in practice exploit the theoretical vulnerabilities of Condorcet
>> methods in real elections.)
>> 
>>> It seems that there is a risk, that Condorcet methods are reduced to
>>> plurality-like methods due to voting strategies that exploit the fact
>>> that FBC and LNH do not hold.
>> 
>> That could happen in principle, but I believe in most environments that
>> would not be the case. And even if that would happen, probably those fears
>> (leading to bullet voting or plurality-like methods) would be irrational.
>> 
>> Juho
>> 
>> 
>> 
>> 
>> 
>> 
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