[EM] The easiest method to 'tolerate'

Fri Jul 1 08:48:52 PDT 2016

On 07/01/2016 12:44 AM, Kevin Venzke wrote:
> Hi Kristofer,
> 
> ________________________________
> De : Kristofer Munsterhjelm <km_elmet at t-online.de>
> À : Kevin Venzke <stepjak at yahoo.fr>; steve bosworth <stevebosworth at hotmail.com>; EM list <election-methods at electorama.com> 
> Envoyé le : Mercredi 29 juin 2016 6h19
> Objet : Re: [EM] The easiest method to 'tolerate'
> 
>>
>> See also, from a Range perspective: http://rangevoting.org/MedianVrange.html
>>
> 
> Unrelated: That link says Chris Benham invented MCA. I'm pretty sure
> that's wrong, and that it was either Forest, or else it didn't have a
> clear inventor. But I am struggling to find any archives for this list
> older than 2015. Hopefully we have not managed to lose nearly 20 years
> of posts...?

http://permalink.gmane.org/gmane.politics.election-methods/184

says it's Forest.

> I'm trimming the below because I can't figure out how to make yahoo quote this:
> 
>> A rational voter would still always strategize because there's no actual
>> harm to doing so, and if enough voters aligned with his candidate think
>> the way he does, he'll benefit. So it's a chance of getting something
>> better with no risk, and a rational voter would take that.
>>
>> However, it seems unintuitive to me that a real voter would do so.
>> Instead, it seems more that voters value expressing their true
>> preference, and as long as the benefit to strategy is less than what
>> they gain by expressing their preference, honesty wins.
>>
>> I have no hard proof that this is the case, and as I mentioned in
>> another post, there might very well be cultural differences. An
>> electorate accustomed to FPTP and the pervasive strategy there might be
>> more inclined to be strategic by default. I also seem to recall that the
>> parties in New York under STV almost immediately tried to game STV
>> through vote management, whereas according to Schulze's paper on vote
>> management, other countries' STV elections seem to be relatively free of
>> strategy.
> 
> 
> If we are reading the same paper, that's not my impression of what
> it said. I thought it said that vote management in particular was widespread.

I must have remembered incorrectly. On a second reading of the paper
(http://m-schulze.9mail.de/schulze2.pdf), I see that he gives general
examples where the voters learn to manage their votes. I was thinking of
the more specific examples he gave in sections 3.1-3.2. where he found
no evidence of Woodall free riding in the Cambridge School Council
elections and no evidence of Hylland free riding (under certain
assumptions) in the same ballot data. However, in section 3.3. Schulze
also says:

> On the other side, we quoted several empirical papers on STV that 
> demonstrate that Hylland free riding is a frequently used strategy (Berger, 
> 2004; Harris, 1930; Johnston, 2000; Pilon, 1994).

and in section 4, he gives examples of vote management in various
countries where STV has been used. So I was wrong; I must have only
remembered the Council free-riding examples.

> I don't disagree with your statements on median rating, but I don't
> quite see the point of messing around with a method like that, whose
> benefits are undone if human nature isn't what we think. Even if you
> manage to adopt it successfully for e.g. a school board election, who's
> to say it will continue to work properly as political stakes increase
> (e.g. moving on to adopt the method for a gubernatorial election). It
> seems hard to advocate.
> 
> Generally I don't think that much is based on culture when it comes 
> to comparative politics. If something is at stake, one should look
> and keep looking for the practical reasons why actors do what they
> do.
> 
> Certainly I have an ulterior motive for thinking this way: If we can
> introduce roles for culture, or the inherent sincerity of voters, then
> it becomes even harder to create a meaningful simulation to try to
> forecast methods' properties.

Yes, I understand that, and I would be inclined to believe that voters
generally won't employ strategy in the kind of thresholded utility
setting I mentioned in the previous post (independent of culture). I'm
mostly mentioning culture because my inclination seems to be greatly at
odds with, say, Ossipoff's. He focuses a lot on compromising strategy,
as well, which seems (sort of) to be based on how prevalent
lesser-of-two-evils voting is in the US. Also, Norway uses party list PR
and I have the impression that tactical voting isn't really a thing here
when talking about parties above the threshold, even though
Plurality-based party list PR has a compromise incentive between seats.

So I could be wrong about culture playing a part. But then some other
explanation has to account for my observations, or I have to be wrong
about some of them as well.

If, on the other hand, voters generally do strategize in threshold
scenarios where there's nothing to lose or gain until a certain level of
strategy, then we're in rather more trouble. One could easily argue that
Condorcet would lead to inferior outcomes because voters would betray
their favorites in that manner. See e.g.
http://rangevoting.org/IRVStratPf.html :

"Strengthening: If could, however, be argued that if the CBA voters are
convinced C cannot win, then their betrayal by switching to BCA cannot
hurt them but with 8.78% probability will help them. I.e, if convinced C
cannot win, then this betrayal is a strategically sometimes-wise and
never-unwise move with 100% probability. "

>> It's always advantageous if the method also makes sense based on how it
>> works, but I'd rather have an opaque method with good compliance than
>> vice versa. Borda is very simple, but its extreme teaming incentive
>> makes it of little use in competitive elections.
> 
> I feel like the value comes not just from understanding how it works
> but being comfortable with how the method behaves as an agent for the
> voter. I've been wanting to write a post for several months on a few
> topics but I haven't found an excuse or even an overarching idea. This
> is one piece though. It's common to think of the method as an agent
> representing the entire electorate, which figures out the best possible
> result for everybody. But we could also try to imagine a given method's
> rules in terms of how we would define an agent representing an
> individual voter, such that the interactions of the agents produce the
> method's results. Think of the agents as legislators talking among
> themselves before making a final vote.

I see what you mean. IRV fits well as an individual DSV method. It's
much harder to do that with Condorcet because Condorcet is "global". I
imagine you could make a sort of probabilistic variant where you vote on
candidates in turn, legislature style, but it wouldn't be strategically
resistant.

E.g. something like

1000 times:
- order the candidates in random order
- ask "do you prefer X or Y" where X is the first candidate and Y is the
second
- whoever wins is then compared to the third in line, and so on.

Pick the winner who won most often.

Then each agent participates by voting for the proper candidate in each
proposal, and the agenda is set to be random so that nobody has an
unfair advantage. But this would most likely reduce to Copeland and so
be full of ties.

Another option is BTR-IRV where the two last by Plurality count get an
elimination round and the pairwise loser is eliminated.

Bucklin could be considered a method where each voter has a reluctance
to voice his support for candidate X, and then as time passes, he adds
inn support he's more reluctant to voice until someone gets a majority.

I suppose that Borda-elimination doesn't feel as well-suited as an
individual DSV method because it's not clear why one is using Borda. If
IRV proponents are coming from Plurality, it makes sense to use
Plurality logic, even though from a logical perspective, it is not
altogether clear why Plurality should be good at finding losers if it's
bad at finding winners.

It's too bad we can't just search over the whole space of
"natural-sounding" rules and find the best one. What does or doesn't
constitute a natural-sounding or pleasing rule is not very clearly
defined, though I do think you're onto something with the DSV explanation.

> There are obvious reasons why we wouldn't want to just use first
> preferences to tell us about apparent viability. But the first
> preferences are the ones we can definitely trust. If we were to accept
> that as important (even if just for sake of argument) I wonder if it
> would lead somewhere.

My brute force attempt to find strategically resistant Condorcet rules
for three-candidate elections did find something that used first
preferences.

If there's no cycle, elect the CW. Otherwise, let A>B>C>A and call the
candidate we're considering A without loss of generality. Then A's score
is fpA - fpC. The candidate with highest score wins.

First preferences can be important since you can't bury with them.
They're not all that important under honesty, however.