Condorcet, a modern voting system

I would like to continue the discussion of voting. One of Tyson’s previous posts illustrated the flaws of the electoral system, particularly the differences in “power” that residents of different states have. The winner-take-all system employed by most states also makes third parties effectively irrelevant. In order to gather electoral votes a third party would need to get more votes than both established parties in a state, which is near to impossible in practice.

These are obvious problems, but I would like to reflect on a more subtle point. I would like to “raise your consciousness” on the voting system itself, and to present an alternative. 

The most used voting system is the plurality voting system, or in layman’s terms, the simple majority vote system. This basically means voters can tick one alternative on their ballot. The candidate that receives the most votes wins (and in the electoral system, all the electoral votes for that state).

The simple majority vote, however, sucks — and there are mathematical reasons for asserting so. The majority vote only reveals an individual’s preferred candidate, but there are other criteria, e.g. the independence of irrelevant alternatives (IIA). That is a fancy way of saying your vote for Perot should not undercut your support for Bush Sr. and cause Clinton to win — or your support for Nader should not enable Bush Jr. to win, which it did, unfortunately for us all…

The simple majority vote system cannot account for such nuances. It forces people to vote — not for the candidate they prefer — but for the candidate who can beat the one they fear most, and as I say, that sucks.

The Condorcet voting method allows each voter to rank all alternatives instead of picking a single candidate. The benefit is obvious: voting sincerely doesn’t force you to waste your vote.

In practice, candidates are ranked from least to most preferred. They may be given equal preference and those left unranked are regarded as equal (but below the least preferred alternative). To calculate the winner all candidates are paired together. 

For example, if Alice is paired against Bob it is necessary to count both the number of voters who have ranked Alice higher than Bob, and the number who have ranked Bob higher than Alice. If Alice is preferred by more voters then she is the winner of that pairing. When all possible pairings of candidates have been considered, if one candidate beats every other candidate in these contests then they are declared the Condorcet winner.

If there is no clear winner, then their are other mathematical models for determining the winner. Check out the link above for more information.

So is this already used somewhere? Actualy yes. Most users can be found in the open source code community, but also Kingman Hall at Berkely, Music Television (MTV) and Wikimedia Foundation to name a few. Have a look at the whole list if you like.


One Response

  1. The condorcet criterion actually isn’t good. Why would it make more sense to elect the person who wins in a very specific tournament-style set of voting rounds? Doesn’t it make more sense to take people’s strength of preference into account? Range voting (aka score voting) does that, and is a much better voting system. Take a look at voter satisfaction scores for condorcet vs score voting here: . The worst case of score voting is almost as good as the best case of condorcet.

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