[EM] Re: majority rule, mutinous pirates, and voter strategy

[James Green-Armytage]

Hi Juho,
	Various replies follow, on the subject of voter strategy.

>Condorcet is close to a dream come true in the sense that it almost 
>provides a perfect solution that eliminates all strategies from 
>elections and frees people to giving sincere votes only. 

	This is true only in terms of the"compromising" strategy, which Condorcet
methods minimize. However, they open the door to the "burying" strategy,
which does not exist in plurality or IRV. I already defined these terms
for you. See also Blake Cretney's web site, for a list of which methods
are haunted by which strategies.
http://condorcet.org/
	The burying strategy is more of a theoretical phenomenon than the
compromising strategy, because methods that invite the burying strategy
are not yet used in large-scale contentious elections. Hence it's hard to
say exactly how common it will be. However, I feel that we can say with
some confidence that it will be more common in some methods than others.
E.g. more common in margins than winning votes; more common in winning
votes than in any of the following: cardinal pairwise, approval-weighted
pairwise, wv with CWO or AERLO/ATLO.
	Have you read my 3/14 post yet?
http://lists.electorama.com/pipermail/election-methods-electorama.com/2005-March/015125.html

>I would like to see concrete examples of cases 
>where in _real_world_election_situations_ strategical voting is a real 
>risk (and opportunity). 

	It's hard to find real-world data about voter behavior given voting
systems like Condorcet that are predominantly theoretical. I suppose we
could try to take ranked ballots from a STV elections and see what sort of
strategic possibilities would have existed if it had been a Condorcet
election instead. That's not quite the same thing, but it might be fun
anyway.

>If such cases are not clearly demonstrated for 
>each strategy eliminating fix/method, then we take the risk of picking 
>an election method that has features that are good in theory but never 
>needed in practice.

	It's far better to err on the side of caution, especially when the
integrity of the electoral process and the credibility of pairwise count
methods are at stake.
>
>
>Summary:  Simple examples of use cases where strategies are a real 
>threat are needed to justify adding such defense mechanisms in the 
>election system.

	I have provided several made-up examples along these lines. If you want
real examples, you have to wait for the method to be adopted for
contentious elections.
>
>Some classifications that may be useful when analysing the seriousness 
>of different voting strategy threats:
...
	Your "a" through "k" code system is perhaps not necessary, but the
questions you are asking are largely the right ones to ask.

>One example strategy that I find interesting (because it is not so easy 
>to ignore) is one where voters try to create a loop that includes only 
>the candidates of a competing party. All voters add at the end of their 
>ballot a list of candidates of the competing party in certain order. Do
>we need to defend against this? 

	Yes, among other forms of the burying strategy.

>What would be the best method? 

	To begin with, the method should be Smith-efficient. That way, if none of
the strategizers' party's (party B's) candidates actually beat the other
party's (party A's) candidates, the winner will come from party A. With
minimax, party A could be a party of clones with a mutual majority, and
still fall victim to party B's strategy.
	Second, the method should at least be a wv method, if not something
stronger (cardinal pairwise, AWP, CWO, AERLO/ATLO, etc.). I've explored
this idea in other places, and will continue to do so...

>(Note 
>btw that there are also methods outside the vote counting phase.  If we 
>make the ballot forms such that voter can only use limited number of 
>preference values (e.g. from 1 to 5) (several candidates can be given 
>the same value), then there is not much space for making such loops.)

	There are better ways to curtail strategy; reducing preference spaces is
not necessary.
>
>Another interesting area is the recent discussion on this mailing list 
>on withdrawal after the elections. This is a very risky case since now 
>everyone knows exactly what the votes are unlike before the election 
>when they probably only had wild guesses and few Gallups.

	The concept of CWO (candidate withdrawal option) is that there is only
one public vote, but after the initial tally, candidates have the option
of having a new tally with their names deleted from the ballot. We can
only hope that the candidates will usually have enough information to tell
sincere cycles apart from strategically created cycles, and that they will
primarily use the CWO to correct strategically altered results. CWO is one
of the more rough anti-strategy measures, but it has the advantage of not
complicating the ballot and keeping the tally method proper as simple as
possible.

my best,
James
>
http://fc.antioch.edu/~james_green-armytage/voting.htm