Range Voting
(RV) leads to more votes for third parties – especially "infant"
parties that are weak – than approval voting (which in turn generates
more votes than plurality voting). This is an
experimental
finding, not a theory.
In contrast, IRV does not generate many
third-party votes.
In Australia's 2004 national election,
there were these
vote fractions by party:
.404,
.058,
.382,
.007,
.004,
.002,
.0024,
.006,
.0012,
.0012
where the .404 and .058 should be merged into a single .462
if you count the Nationals & Liberals as "one" party as is usual.
This is then 0.7% max vote percentage for any third party and
2.4% for all third parties combined. (These numbers are
from the top-rank vote counts in IRV voting.) Compare with the USA's 2004
election where all third-party presidential candidates got a bit under 1% of the
vote combined.
The seat-counts that resulted in this election were
87, 60, 1, 1, and 1 for 150 total seats in Australia's
federal lower house.
Vastly
more third-party votes – multiplicative factors of 10-50 relative to the vote-counts
of the top-finishers – can happen
with range than the closely-related approval voting system.
We believe we understand why this happens – it comes from strategical
reasoning by the voters (which differs under different voting systems)
combined with psychology. Essentially, more voter "honesty" is more
reasonably possible under range voting, as opposed to Approval and other voting systems
which frustrate voters' honest desires to support third party views.
And this experimental finding is not just because humans are irrational; it actually
makes logical sense. Why?
If an 0-99 range voter has given 0s and 99s to the candidates
she considers most likely to win, and now asks herself "how should I score the
remaining no-hope candidates?",
the strategic payoff for exaggerating to give them 0s or 99s can easily be extremely small,
because the probability of that causing or preventing them winning can easily be below 10-100.
Supposing a voter gets even a single molecule worth of "happiness neurotransmitter"
from voting honestly on these candidates, that happiness-payoff
is worth more to that voter than the
expected payoff from exaggerating about these candidates via "approval style" range-voting.
Therefore, range voters will often cast substantially-honest range votes, even those inclined to be
"strategic."
We call this the "nursery effect" since it "shelters helpless infant"
third parties allowing them to grow. Once parties grow big and strong,
RV "kicks them out of the nursery" – there is no longer any big difference
between Approval versus Range vote-totals for candidates from big (including big third) parties.
This effect may be so strong that Approval Voting will still lead to
2-party domination just like plurality voting. We don't know.
But clearly RV has a far greater chance of allowing third parties to
grow to the point where they can be important.
Also, removing the
blank-score (X)
option from
range voting asymmetrically hurts third parties
because fewer voters are knowledgeable
about third parties, hence more voters X those scores ("no opinion")
and if those Xs were no longer treated as Xs, but instead as the lowest
possible score 0, then that would hurt the third party candidates. Meanwhile
almost all voters have opinions about the major-party candidates – so that for
those parties this X policy choice has almost no effect.
This has the very important consequence that
only range voting (preferably with blanks)
can hope to garner unified third-party support
and hence only RV can lead to voting
reform.
So for voting reform advocates
it is a matter of survival: you must push range voting.