Range Voting, aka Score Voting
(SV) 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
finding, not a theory.
In contrast, IRV does not generate many
In Australia's 2004 national election,
there were these
vote fractions by party:
and many below that.
where the .405 and .059 should be merged into a single .464
if you count the Nationals & Liberals as "one" party as is usual.
This is then 7% max vote percentage for any third party and
13% for all third parties combined. (These numbers are
from the top-rank vote counts in IRV voting.) Compare with the USA's 2000
election where all third-party presidential candidates got a bit under 4% of the
vote combined; in 1992 it was about 19%.
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 (the 1s are Independents).
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 score 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 score 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" score-voting.
Therefore, score voters will often cast substantially-honest score votes, even voters
inclined to be
We call this the "nursery effect" since it "shelters helpless infant"
third parties allowing them to grow. Once parties grow big and strong,
SV "kicks them out of the nursery" – there is no longer any big difference
between Approval versus Score 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 and instant runoff voting (IRV). We don't know.
But clearly SV has a far greater chance of allowing third parties to
grow to the point where they can be important.
Also, removing the
score 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 score voting (preferably with blanks)
can hope to garner unified third-party support
and hence only SV can lead to voting
So for voting reform advocates
it is a matter of survival: you must push score voting.