[EM] Strategy-proof vs Monotone

[Richard Lung]

km,
You are repeating what the rest of my post already says -- the need for testing in realistic scenarios. -- Not so much to test monotonicity and strategy resistance. That is guaranteed by the removal of the ad hoc premature exclusion of candidates. And replacing it with an exclusion count, symmetrical to, or exactly the same as the election count,  That is a transferable vote, known to be monotonic -- and hence so, in an exclusion count as well as an election count.
I have actually given the odd example for illustrative purposes, which shows that when you swap preference transfers, it can never create a strategy incentive. That is because preference changes are always accompanied by a change in the respective candidates keep values. There is proper book-keeping of the electoral accounts!

You should be prepared to be surprised. Being surprised is no argument.

You raised a much more pertinent criticism of binomial stv, which needs to be tested by trial elections, to which I wrote an answer, not to hand. In any case trials would be good, instead of preconceptions, if it's not asking too much.

Richard Lung.



On 19 Jan 2022, at 6:59 pm, Kristofer Munsterhjelm <km_elmet at t-online.de> wrote:


> On 19.01.2022 19:48, Richard Lung wrote:
> 
> Treating an election as a statistic, binomial stv is monotonic and
> strategy-resistant. I would guess that all run-off methods, which
> actually includes traditional stv, are non-monotonic, in principle.

Unfortunately, without an implementation, I can't verify that claim; and
since no STV method I've seen so far have been proven to be monotone, I
would find it surprising if this were the case.

It would of course be good if it were true! But I have no way of
determining that.

-km