[EM] Margins vs. Winning Votes

[James Green-Armytage]

Juho Laatu writes:
>Thanks for the comments.

	You're welcome!

>I think the correct way forward would be to write those examples down 
>and then see what we have and estimate then relative vulnerability (of 
>winning votes, margins and pair-wise methods in general) to strategies.

	Seems a bit too anecdotal. It's hard to quantify vulnerability. A
computer simulation might somewhat interesting numerical data, but the
result depends on what kind of assumptions you put into it. So far, I
think that intuitive reasoning is a more useful way to approach this topic
than any quantitative method that I can think of.

>I think the main battle should be fought already before the 
>counterstrategies will be applied. I mean that normal voters would 
>probably be unable to understand and apply counterstrategies and having 
>to deal with them would give a bad impression of the voting method. I 
>tend to think that if people would need to stop voting sincerely and 
>start using strategies and counterstrategies, it could be better to 
>forget that voting method and use some simpler method instead (IRV?, 
>approval?, two round runoff?). I'm however living in the hope that 
>pair-wise comparison methods would in most cases be strategy free 
>enough so that voters could trust the method and vote sincerely 
>(without being afraid that the few remaining strategic voters (there 
>will be some in any case) could get their way through).

	Right... it's a difficult issue. In my opinion, cardinal pairwise (and to
a slightly lesser extent, approval pairwise) does a better job than WV at
allowing voters to vote sincerely without having to worry much about
strategy. But these methods are perhaps too complicated for a first
generation proposal.
	How complex is the counterstrategy in WV? Basically, if you prefer X>Y,
and you don't trust the Y>X voters to refrain from trying to bury X, you
shouldn't rank Y above any other candidate. To be honest, I don't know how
well this would work in practice, i.e. whether voters would be comfortable
using the counterstrategy, how often successful incursions might occur,
and how often strategic truncation might obscure a sincere Condorcet
winner. However, I would much rather implement WV than margins, as I
consider the latter to be truly unstable. 
	On the subject of public salability, one could argue that the
Smith-efficient Condorcet methods with WV or margins are too complex for a
first generation proposal. It depends to whom the proposal is being made,
and for what purpose. If a Smith-efficient WV method is too complex for a
given function, I am happy to start with approval or IRV (preferably
ER-IRV, and CWO-IRV as a very ambitious proposal), in the hopes that
smaller steps will eventually lead to greater ones. I'm also interested in
non-binding ranked ballot direct democracy systems that uses a pairwise
tally; I expect that this would help make the concept of a Condorcet
winner more concrete and intuitive to the general public.

>One difference between the examples is that in my example Democrats 
>left Republicans unranked while in your example Democrats always rank 
>Republicans and Republicans themselves don't express opinion on "C vs. 
>A". The former looks more probable in real life. Or maybe there are 
>cases where also the latter type of partial ranking is common(?). Do 
>you have some "real life explanation" why people voted like they did?

	I think that my example works more or less the same if some of the
Democrats truncate in the initial rankings.
	I find it fairly realistic that some moderate Republicans (B voters)
would not want to rank the more extreme Republican.

>I should also calculate how easy/difficult it is to apply the different 
>strategies (number of votes needed, risks etc.) but that's too much for 
>now and I leave that for further study.

	Again, I doubt that quantitative analysis will yield a satisfying result,
but there is no harm in trying.

>As already noted I don't like counterstrategies (in real life 
>elections). I however think the anger of the B voters is justified. B 
>voters however don't win anything if they manage to make A the winner 
>(unless one considers revenge as one type of victory :-). The game 
>appears quite tricky if both B and C voters apply strategies and 
>counterstrategies and try t react each others' anticipated voting 
>behaviour.

	This may be obvious to you, but I should mention it to avoid confusion.
If B>A voters are worried about the A>B voters trying to bury B, their
truncation counterstrategy in WV is only useful if they are able to make
it clear to the A voters that they will use it. That is, the information
should come out in pre-election polls, or something like that. If it
doesn't, then its deterrent value is lost, and its value to the B voters
is questionable. Of course, the B voters can't wait to see what the A
voters do before they decide to use the counterstrategy.

>Rather than recommending use of strategies 
>and counterstrategies I hope that strategies are unusable enough to 
>allow people to vote sincerely. Maybe lack of exact information on how 
>people are going to vote and dislike of strategic voting and voters 
>will do the job.

	Maybe, maybe not. If a lot of the A voters in an example similar to mine
are A>>>>>>>>>B>C voters (huge utility gap between A and B, negligible gap
between B and C), there is very little incentive against their trying to
bury the candidate whom they consider to be A's closest rival, i.e. the
one most likely to beat A in pairwise comparison.

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