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No System is Perfect ...
July
2002
... but choice voting (single
transferable vote, STV) works pretty well.
A brief, non-technical
response to mathematical critiques of choice voting
Some people criticize the
choice voting form of proportional representation because in certain
very limited circumstances it is at least theoretically possible
for choice voting to lead to the election of a candidate that
common sense suggests should not be elected.
Why is this not a fatal
problem for choice voting?
Because these kinds of situations can occur
with all voting systems, but
in the real world, these situations never actually occur in choice
voting elections. For examples of the types of
situations in which different voting systems suffer flaws, check
out these
examples and judge for yourself which ones would be likely to
occur in actual public elections.
Kenneth Arrow won a Nobel Prize in 1972 for showing,
in effect, that no voting system is perfect. If you choose a
few reasonable criteria, such as the majority should rule and voting
for your favorite candidate should not help your least favorite
candidate, Arrow showed that all voting systems violate some of
these criteria some of the time. A voting system that meets
all of the criteria all of the time simply does not exist.
Thus, when someone points out that
a particular voting system in a particular situation leads to an
undesired response, we must ask, "Does this problem only occur in
theory, or does it actually occur in real word elections?"
Choice voting actually
works
Choice voting has been used in
public elections for over 100 years in the US and around the world,
and we have not uncovered even a single example where any of the
theoretical defects have occurred.
This includes tens of thousands of
elections with tens of millions of voters. If the theoretical
problems with choice voting occurred even as frequently as 0.1% of
the time, there would be many such examples, but there are none.
Choice voting allows voters to
vote sincerely for the candidates they actually support, most voters
end up being represented by their preferred candidates, and the
outcome is broadly representative of the entire electorate.
Kenneth Arrow showed that all
voting systems can be "gamed" in certain situations. The
situations in which choice voting can be "gamed" are so infrequent
as to be virtually undetectable, and if a voter ever tries to game
the system, rather than voting sincerely for her preferred
candidates, she is far more likely to shoot herself in the foot than
help her cause.
A couple academic references
"Single Transferable
Vote Resists Strategic Voting," Social Choice and Welfare,
1991, 8:341-354.
This articles shows
mathematically that choice voting is virtually impossible to
manipulate, which explains why no real world example has ever been
found. The only examples people raise are highly unrealistic,
artificial ones.
Crispin Allard, "Lack of Monotonicity - Revisited,"
Representation 33 (1995):49.
As Professor Amy writes in Behind the Ballot Box,
referring to the Allard paper, "One statistical study founded that
if STV elections were to be held through the United Kingdom, a
nonmonotonic result would occur less than once a century."
Monotonicity just means that voting for your favorite candidate
shouldn't help your least favorite candidate. It's
theoretically possible that voting for your favorite candidate in
choice voting could help your least favorite, but as Allard shows,
this is very unwise strategy in choice voting.
Conclusion
Choice voting allows all voters to vote sincerely for their
favorite candidates, and the winners fairly represent as many voters
as possible. No system is perfect, but choice voting works
very well. |
