[Election-Methods] RE : Corrected "strategy in Condorcet" section

[Juho]

On Aug 10, 2007, at 5:53 , Kevin Venzke wrote:

> I think margins does give a clear reason to not vote for weak  
> candidates,
> especially if there's a chance they're strong enough to get a pairwise
> win.

I still miss the concrete waterproof example. (Sorry if I should have  
known which one it is.)

truncation...
> I don't know what the number of candidates has to do with it.

If there are e.g. 100 candidates then I can understand that voters  
truncate even if they have no strategic intentions and even if they  
have an opinion on the relative preference of some of the less liked  
candidates / unlikely winners. Listing all 100 candidates would be  
too much and too boring for them.

...
>> Ok, that means bullet voting for the strongest.
>
> I'm sorry what? I'm talking about adding functionality to FPP, not  
> using
> a certain strategy under FPP.

Sorry for the unclear linking, I referred to the Condorcet wv  
strategy proposal that was discussed before the last paragraph (that  
talked about FPP).

>>> I would say under plurality very few people vote sincerely, and
>>> those that
>>> do mainly vote for candidates that we wouldn't expect to become  
>>> viable
>>> anyway, even if it were safe to vote for them.
>>>
>>> Even with a top-two runoff I think you see a lot more sincerity
>>> than under
>>> FPP.
>>
>> Yes, my experience with top-two runoff is that most voters vote
>> sincerely. I think I have not heard anyone saying that they would
>> have voted strategically, nor have I seen recommendations to vote
>> strategically. I think I have seen one strategic nomination when the
>> far left party didn't name their own candidate for the election but
>> nominated the moderate left candidate as their candidate. Top-two
>> runoff can be said to be at least as vulnerable to strategic voting
>> than Condorcet. If the two-round runoff would be changed to Condorcet
>> I'd expect the sincere voting tradition to continue. Your background
>> may be different and different countries and political systems may be
>> different but I think there are places where Condorcet could be used
>> successfully and practically without any strategic voting. The
>> theoretical problem cases exist, but they do exist in two-round
>> runoff as well, and people don't seem to mind.
>
> Well, in a two-round runoff you might want to vote strategically in  
> the
> first round if you fear that neither of the top two candidates will be
> any good. If you're not afraid of that then why not vote sincerely?

Yes, some people may give up voting their first choice at the first  
round if they think they have no chance of winning. It however  
appears that majority of the voters have stuck to their most  
preferred candidate also at the first round. I don't have exact  
numbers here but according to my understanding the weaker candidates  
have not dramatically lost votes at the first round. There may be  
also voters that vote one of the weaker candidates just to show that  
the frontrunners are not as good as they think they are. And the  
supporters of the weak candidates may live in the hope that in the  
next election they will win. Or they may show support to their party  
since that may increase the votes or keep them at the same level in  
the next proportional elections. The last point may be quite  
important in a multi-party system (since small parties want to stay  
alive).

That last point may also play a role in ranked elections. There may  
e.g. be many left wing voters who what to make it clear in the  
election results that they preferred all the left wing parties over  
the right wing parties, and centrists over the extreme right etc.  
They may fear that if they start slipping, that might become a trend  
(in the next whatever elections).

> I think if you converted a two-round runoff into IRV where all but the
> top two candidates are immediately eliminated, you'd immediately see
> a major hit to sincerity. More importantly I think, you'd see a  
> major hit
> to the number of candidates who can get votes.

See comments below ***.

>>> I
>>> keep pointing out that WV consistently avoids favorite betrayal
>>> incentive in these situations, and in response you point out that in
>>> margins, one faction here shouldn't have truncation incentive. If
>>> margins
>>> consistently has that quality then sure, that would be noteworthy.
>>
>> I think all the vulnerabilities are equal.
>
> I don't. If a vulnerability won't occur to a voter to use, it's not as
> important. If the vulnerability doesn't harm the result or even  
> makes the
> result better, it's not as important. Etc.

Ok, vulnerabilities are not equal if the threat level, probability,  
damage etc. are different, but the name of the vulnerability type  
doesn't matter if te other parameters are "at the same level".

>> Yes, I meant sincere voting in Condorcet. I don't believe I can
>> provide you a method that would be immune to strategic voting, but I
>> do believe that in some environments most people would vote sincerely
>> anyway. This is because on average sincere voting can be claimed to
>> bring them the best results.
>
> This is not really true with respect to votes for candidates that  
> you do
> not think can win.

True for candidates that have no chances. Giving few additional votes  
to some (non-winning) candidate might however have some impact in the  
next elections.

>> Hunting for the not so common and not so
>> certain strategic opportunities and then taking part in such "plots"
>> may not be tempting to them. I have seen relatively sincere behaviour
>> in two-round runoff too, so why not in Condorcet. The strategies are
>> a bit different but maybe not that much different.
>
> Two rounds. If you split a Condorcet method into two rounds I think  
> you
> will get more sincerity, since more candidates could be considered
> viable, and voters have a chance to adjust for mistakes that they
> otherwise couldn't react to.

*** Having two rounds doesn't sound dramatically different to me.  
Many voters will anyway vote according to the preference order that  
they used already at the first round.

>> I note that in addition to discussing the vulnerability of margins
>> vs. winning votes and their other weaknesses and strengths we now
>> have also the environments with wide spread strategic voting and
>> marginal strategic voting on the table. Answers to the first question
>> in these two environments may be somewhat different.
>
> If you assume sincere voting then you just don't have to deal with
> arguments about negative incentives.

I meant predominantly sincere. Strategic voting may emerge if there  
are some good reasons for that, but in the absence of any clear  
reasons to vote strategically people would tend to vote sincerely.


I think we would need more real life use cases to see how  
strategically people will behave in real life and in different types  
of political systems. The two-round runoff cases may give some  
indication but the do not yet guarantee that people would behave the  
same way with Condorcet.

Juho




	
	
		
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