[EM] Approval Voting vs Instant Runoff Voting:

[LAYTON Craig]

Mike wrote:

>As I recently just finished saying here, every pairwise preference that you

>vote in Approval is reliably & fully counted. In what sense, then
>do you claim that no one's vote counts? Or that the ordinary voter's
>vote doesn't count?

For a while I've been saying that preferential systems standardise voting
power, which is important in giving voters an equal say.  Approval does not
do this.  Here is what I mean;

<please note: I'm not arguing that IRV is better than approval, simply that
I don't find approval acceptable>

There is a four candidate race.  There may be more than four candidates, but
only four are "contenders".  The race is very close between all four
contenders, and opinion polls are neck and neck.  

the ballots are
A 20
B 14
C 13
D 23
AB 10
CD 10
BCD 5
ABC 5

the results are
D 38
A 35
B 34
C 33

D is elected with only 38 percent of the vote.  The result is worse than an
IRV election, in which you can at least be certain that the winner has won
at least one pairwise contest against another candidate.  In this approval
election, you could well be electing the Condorcet loser.  Many voters waste
their vote, because the information available (showing the candidates equal)
wasn't sufficient enough to tell them how many candidates they should vote
for to maximise their voting power, assuming that ordinary voters have the
inclination or capacity to process this information in anything other than a
two horse race.  Relying on strategy for your voting system to work is
highly fallable.

Quite a few voters vote for only one candidate.  I don't see this as an
exaggeration.  I'm sure that you can imagine a four candidate race where
your utilities are such that you would bullet vote.  If you're a left-wing
American, I guess it would be a race between a democrat, republican, reform
and then someone even more right wing than that.  In Australia, I can
imagine the race to be between Labor, Liberal, National and One Nation.  In
that order, my sincere estimated utility value (out of 100) would be
something like 100, 25, 20, 0.  It would not be unreasonable to suggest that
I vote for only the "100" in such a scenario.

The approval example isn't too unrealistic.  It could be worse.