[EM] Realistic strategy questions

[Jameson Quinn]

I have been working on my program for measuring the Voter Satisfaction
Efficiency (formerly known as BR) of various systems. It's just about ready
to do a big run, but before I do that, I'd like to get as many of the
activists here to say what they think are reasonable settings for
generating scenarios. In particular, I have to decide proportions for
various kinds of strategic voters.

Here's a few possible kinds of voters:

   1. Honest: Will always map their utility onto a vote as honestly
   (linearly) as possible, after normalization over the range of candidates
   available.
   2. Media-based Honest: As above, but when normalizing, they will ignore
   all candidates who are worse than both polled frontrunners.
   3. Fully strategic: Will always strategize by maximizing the ballot
   distance between the two (honestly) polled frontrunners.
   4. Weakly strategic: Will strategize, but only as much as "necessary".
   That is, assuming no other voters strategize, they will shift their vote,
   focusing on the margin between the polled winner and runner-up. In a
   Condorcet system, such a voter would always be honest. In a median system,
   they would exaggerate to ensure they graded the winner and runner up on
   opposite sides of both of their polled total grades, but not necessarily to
   an extreme; so if their honest vote was A,B,C,D,F and the polled grades
   were D,C+,C-,D,D, then they'd vote A,B,D,D,F.
   5. Lazily strategic: Fully strategic if and only if their weakly
   strategic vote would not be identical to their honest vote.
   6. Threshold strategic: Fully strategic if and only if their utility
   (satisfaction) difference between the polled frontrunners is greater than
   some threshold (in absolute value)
   7. One-sided strategic: Will strategize if and only if they prefer the
   polled runner-up to the polled winner.
   8. 20/20 hindsight: Fully strategic if and only if one of the last N
   election results was changed by strategy. (When simulating, you'd just use
   some constant probability for each election system, and find an equilibrium
   point for that probability).
   9. Sheep: strategic iff more than X% of the non-sheep voters are.
   10. Cliquish: Certain probability of being each of the above kinds,
   except with a certain extra probability of being the same as other voters
   who share similar utilities.

Obviously, it would be easy to extend the above list by combining the
various aspects there.

Personally, I find ALL of the above strategic types to be essentially
plausible. I know that the full decision rule for some (such as weakly and
lazily) are more complex than the explicit thought processes of 99.99% of
voters, but in practice I think it would be easy to end up acting like that
through implicit and/or subconscious heuristics. Thus, in particular, I
find it extremely IMplausible that the electorate would consist only of
types 1 and 3, as previous BR simulations generally assumed.

The question, then, is: how many of each kind of voter should I put in? Of
course, I'll run several scenarios, but there's no way I can fully explore
the 8-simplex of possible combinations of the above 9 voter types. So I
have to choose where to focus my attention.

And furthermore, I think it's valuable to say which percentages you find
plausible before you learn how your favorite voting system does under those
percentages. In my debugging so far, I've gotten a glimpse of the impact of
types 1, 3, 4, 5, and 7 above; but I have not looked at the rest at all. So
here's a scenario I find reasonable, and which I really don't know how it
will turn out for my currently-favorite systems:

Each voter has a "honesty type" which are 50% honest and 50% media-based; a
"strategy type" which are 75% full and 25% weak; and a "decision type"
which are 30% hindsight (N=1-3), 30% threshold (X=0.5-2 SD), 20% lazy, 10%
one-sided, 5% always-honest, and 5% always-strategic. They use their
"decision type" to decide whether to vote according to their "honest type"
or their "strategic type". Cliquishness is around 70% (note that even at
that high level, there are good chances of a scenario where the
cliquishness does not lead to one-sidedness).

What do others think is a reasonable scenario? I'd particularly like to
hear from Clay. Clay, I know we're likely to disagree over the meaning of
my VSE numbers once I have them ready; and, only human, we'll probably both
tend to rationalize to make our points. I think that it will help
ameliorate that disagreement if we undercut those future rationalizations
by each precommitting to take our own chosen set of numbers seriously, even
if those are two separate sets of numbers.

Jameson
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.electorama.com/pipermail/election-methods-electorama.com/attachments/20140224/62bf2c27/attachment-0002.htm>