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

[Juho Laatu]

Hello James,

As more or less promised, here are some comments on the rest of your 
mail.

BR,
Juho



3. Condorcet and strategies

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. Ok, there is 
the problem with the loops and there are no strategy free election 
methods. But when comparing Condorcet to many of the methods that are 
commonly used today I would claim that Condorcet solves >90% of the 
strategical voting problems. Being strategy free is thus a key 
requirement. But is it already solved if Condorcet methods are used or 
do we need further protection?

The remaining <10% of the problems (~= "the loop cases") need further 
attention. Out of these <10% some problems are incurable. For the 
remaining ones my approach is such that in order to avoid "shooting 
flies with artillery" I would like to see concrete examples of cases 
where in _real_world_election_situations_ strategical voting is a real 
risk (and opportunity). 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 is possible that the strategies against which we are protecting 
ourselves are not used in practice and the voters simply give us their 
sincere preferences. In such situations the strategy protection 
supporting method may actually give an outcome that deviates from the 
ideal solution that we would have picked if we had trusted all (or most 
of) the votes to be sincere (I'm writing in parallel a reply to Mike 
Ossipoff => some more notes there). These cases are naturally quite 
marginal, but that is just the point => playing with marginal threats 
that change the outcome will probably make the system more complex and 
could even make the outcome worse in some (marginal) situations. If we 
believe that certain voting strategies, although possible, are not 
probable, it may be worth considering leaving those strategies out of 
consideration when planning the best system.

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'll write one very basic use case to show what I mean.
"There are three parties of equal size and one candidate from each 
party. There is a possibility for a single voter to try to bury one of 
the two non-favourite candidates. But the voter has no idea which one 
to bury. => She will vote sincerely. => This use case doesn't seem to 
set new requirements on adding strategy elimination mechanisms."

Some classifications that may be useful when analysing the seriousness 
of different voting strategy threats:

How detailed information of the voter opinions does the voting strategy 
need before it can be efficiently used?
a1) complete set of preferences, a2) detailed, a3) statistical, a4) no 
information needed

Is the strategy useful when the number of voters is b1) small, b2) 
large?

Is the strategy useful when the number of candidates is c1) small, c2) 
large?

Can the strategy be applied d1) independently by individuals, d2) only 
by coordinated groups

Is the strategy e1) same for all, e2) different for different 
individuals ("I vote this way, you vote that way and he votes that 
way")

Can the strategy be applied f1) secretly, f2) will the strategy be 
noticed after the elections, f3) noticed before the elections, f4) 
already known and guessed by all?

g) Are there counter strategies or defensive methods that can be 
applied by others?

h) Is the strategy morally acceptable to people? Of course we often can 
not start judging and don't even know which opinions are sincere and 
which not, but there are cases like "if all would start doing this, the 
whole election would be a mess", "I don't want to admit that I did so", 
"I voted strategically since I expect everyone else did so, and it 
would be therefore stupid not to do so, and lose the elections".

What is the risk of strategy i1) turning against me, i2) having no 
effect?

j) How easy to use?

k) How easy to explain to voters?

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. I 
think this case is a4 (quite bad), d2 (this makes the risk smaller), e2 
(someone votes "ABCDE" someone else "DEABC"), maybe f4, g => everyone 
else does the same, i1=0 (bad), i2 very high but lower if well 
coordinated, j not easy, k not easy.

Do we need to defend against this? What would be the best method? (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.)

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.


I think this is enough for now. Have to rush to other business again. I 
didn't yet comment many things properly like the cardinal pairwise 
method (interesting although I haven't any firm opinions yet). I hope I 
didn't miss too many points where you would like to squeeze and answer 
out of me. :-)