OLPC Europe/Condorcet Method

The "Condorcet Method" is a single-winner election method. In modern examples, voters rank candidates in order of preference. There are then multiple, slightly differing methods for calculating the winner, due to the need to resolve circular ambiguities—including the Kemeny-Young method, Ranked Pairs, and the Schulze method.

Use of Condorcet voting

Elections with the Condorcet Method can be held online here (Cornell University). Condorcet methods are used by a number of private organisations. Organizations which currently use some variant of the Condorcet method are:

• The Debian project uses the Schulze method for internal referendums and to elect its leader [1]
• The Gentoo Linux project uses the Schulze method [2]
• The Software in the Public Interest corporation uses the Schulze method to elect members of its board of directors
• The Free State Project used Minimax Condorcet|Minimax for choosing its target state
• The voting procedure for the United Kingdom|uk.* hierarchy of Usenet

Summary

• Rank the candidates in order (1st, 2nd, 3rd, etc.) of preference. Tie rankings are allowed, which express no preference between the tied candidates.
• Comparing each candidate on the ballot to every other, one at a time (pairwise), tally a "win" for the victor in each match.
• Sum these wins for all ballots cast. The candidate who has won every one of their pairwise contests is the most preferred, and hence the winner of the election.
• In the event of a tie, use a resolution method described below.

A particular point of interest is that it is possible for a candidate to be the most preferred overall without being the first preference of any voter. In a sense, the Condorcet method yields the "best compromise" candidate, the one that the largest majority will find to be least disagreeable, even if not their favorite.

Example

Let's say, the voters have the decide for one winner between A, B, C, D and "None". The ballot paper could look like this (blank):

[ ] Option A
[ ] Option B
[ ] Option C
[ ] Option D
[ ] None

Each voter can rank the options (1 for most preferred), and it is possible to assign the same ranking for more choices. For example:

[3] Option A
[2] Option B
[2] Option C
[1] Option D
[4] None

In this case, the voter would prefer D, followed by either B or C (ranked equally). Third choice is A and None is the last one.

References

• http://en.wikipedia.org/wiki/Condorcet_method
• http://en.wikipedia.org/wiki/Schulze_method
• http://www.debian.org/vote/index.de.html
• http://www.cs.cornell.edu/andru/civs.html