[EM] Some brief campaign argument

LAYTON Craig Craig.LAYTON at add.nsw.gov.au
Mon Apr 16 19:24:33 PDT 2001

This is my post on why you shouldn't vote for Approval in the upcomming
election.  I apologise for the negativity in advance - I didn't have enough
space to throw in arguments in support of Ranked Pairs or BeatPath (or SSD).

There seem to be three main reasons for believing Approval is the best
electoral method - 1) a sincere vote is always the best strategic vote; 2)
approval elections will elect a higher SU winner than any other method/s in
a real world scenario.

(There may be a further reason, that approval is the most mathmatically
consistent method, but on its own, I don't find this argument persuasive.
Please let me know if you do, and why.)

1) Approval is unique in that a sincere vote is always the best strategic
vote.  However, this is because you are only allowed to express a single
layer of preferences - if you're preference is A>B>C, you can only express
the preference A>B or B>C (in addition to A>C).  If you choose to express
A>B, the system forces you to express B=C, even though this may be far from
your sincere preference.  It is only a severe restriction on the preferences
you can express that gives Approval this property, so I don't see it as an

2) Issues of Social Utility are perhaps more complex than game theorists
would have us believe.  If everybody uses sophisticated strategy and/or if
everybody uses an above mean (zero info) strategy then it is true that
Approval would do slightly better on average in electing the highest SU
winner.  Arguments that voters will use highly sophisticated strategies are,
I feel, a little optimistic.  Of course, it is a little irrelevant - zero
info strategy is the most intuitive, and most likely type of voting, and
will still result in a higher SU candidate than Condorcet.  Right?

Maybe, but I suspect not.  In a country with plurality voting, approval
might not change voting habits at all and the vast majority might continue
to vote for just one candidate.  This is by no means fanciful - I consider
it likely among voters who don't understand the system very well (and
perhaps even those who do).

Okay, it's a learning curve and over time, voting habits will change.  When
the voters finally cotton on to what's happening, will they vote for above
mean candidates?  There are still many things that might happen.  Approval
leaves the way open for "vote for everyone except X" type campaigns, where
the result of the election may bear no resemblance to the highest SU winner
whatsoever.  In fact, any elections where the voters vote for too many or
too few will result in a decidedly non-utility maximising outcome.  On the
whole, I find no evidence to suggest that Approval will, on average, find
the SU winner more often than a Condorcet system.  The examples that "prove"
approval will, are based on unreasonable assumptions.

I may go onto Cardinal Ratings, or discuss Approval's only advantage - its
simplicity, in another post.

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