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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.


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