[EM] Approval Voting and Long-term effects of voting systems

[Daniel LaLiberte]

This message is about two related subjects:

1. Factoring in the long-term emergent effects of each voting system.
2. An example of how Approval Voting results in better long-term effects.

Among the many criteria for evaluating voting systems (
https://en.wikipedia.org/wiki/Voting_system#Evaluating_voting_systems_using_criteria)
I don't see any that address the long-term effects of using each voting
system.  In other words, the effect on one election is certainly important,
regarding the satisfaction of the election results by voters and
candidates.  But I would argue that it is even more important to consider
the long-term effects that emerge when applying a voting system repeatedly
over many elections.  A small bias one way or another may not be very
apparent if you only look at one election, but over may elections, they can
add up and perhaps compound the bias exponentially.

There are many long-term effects to consider, but in particular, I am
thinking of one pernicious problem: the tendency for two major parties to
emerge and dominate all politics which results from the repeated
application of plurality voting.  This problem is fairly easy for most
people to understand, although I am surprised to see that there seems to be
a lot of denial about this effect as well.  Some would even defend having
only two major parties, or very few parties.  That is an interesting
subject to discuss, but regardless, I believe we should be aware of how our
choice of a voting system will affect things over time, how society is
likely to evolve based on the rules we lay down, and in fact, how it is
actually very likely that the dominant forces in society will quickly and
vociferously defend whatever rules resulted in their rise to dominance.

But back to this one question, studies and long-term experience have shown
that other voting systems besides plurality, in particular IRV, also result
in the dominance of two major parties.  This may be more surprising to
people, but looking at the underlying cause, it seems we can make a rather
important simplifying argument about most voting systems regarding this
problem. I would assert that the underlying cause of this problem of
two-party dominance in any voting system is that it gives voters the
ability to rank or order at least one candidate higher than the rest.

The reason this ability to rank candidates becomes a problem is the spoiler
effect, where voters will have a strong motivation to give their highest
rank to one of the leading candidates. If they don't, then they weaken the
chance of that candidate winning and therefore strengthen the chance of the
less preferred leading candidate.  Because one of the leading candidates is
likely to win, all the rest of the rankings of non-leading candidates
hardly matter at all.

In any election, there will be two candidates who are the strongest in
terms of popular support, and thus the most likely to win. Consequently (to
grossly over-simplify the process) with any voting system that permits
ranking, groups of voters will tend to coalesce around support for these
two leading candidates to encourage everyone to support their preferred
leading candidate. Eventually two major parties arise, and everyone who
doesn't join one of these two major parties is excluded.

So once voters and candidates figure this out, any such voting system ends
up devolving into the dominance of two major parties that we get with
simple plurality voting.  In fact, one might argue that plurality voting is
better just because it is simpler.

But Approval Voting avoids this problem. Equal-rank approval votes mean
voters don't get the option to express their preferred ranking, but because
of that, they aren't at all motivated to bias their ranking dishonestly.
They only have to decide which candidates to approve, or where the cut-off
is between approval and disapproval.

Given that there are, as before, two leading candidates, how does Approval
Voting affect whether one of those two leading candidates will win?  One of
the two leading candidates is likely to win even with Approval Voting, so
it would appear there is no benefit, but that would be a short-sighted way
to judge a voting system.  In subsequent elections, it would seem likely
that more candidates will run who have broader appeal to ALL voters, not
just a majority or plurality. Because the winning candidates will be those
who are most approved of by the most voters, there will be no value in
parties that typically focus on appealing to no more than half of the
voters.

So I suspect the long-term use of Approval Voting would be self-correcting
toward better and better representation of ALL voters, not just half the
voters, because in each election, almost all of the voters contribute to
choosing the winning candidates, and that only gets better over time as the
candidates who decide to run get closer to receiving the approval of all
voters.

Can any other voting system claim a similar long-term effect?  Even a
voting system with three ranks, e.g. Approve, Neutral, Disapprove, would
encourage voters to approve one of the leading candidates, and give neutral
or disapprove votes to the rest.  I wonder if Approval Voting might be the
ONLY system that has this long-term effect.

What I am aiming for is a voting system that self-corrects over time.  No
matter what voting system we choose, there is probably always going to be
at least some small bias, some inequities or incompleteness.  So we need to
understand this and deal with it.

But one important question should not be overlooked: What do we want to
self-correct toward? That is, what is the long-term goal? I believe we
should want to move toward a closer or better representation of society as
a whole, but there are other ways to look at that.

Looking forward to reading your feedback.

--
Daniel LaLiberte
daniel.laliberte at gmail.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.electorama.com/pipermail/election-methods-electorama.com/attachments/20161121/86e164f1/attachment-0001.htm>