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. :-)
---- Election-methods mailing list - see http://electorama.com/em for list info
