Friday, April 23, 2010

The three-party voting paradox

Take a closer look at the mathematics behind a three-way race – and particularly at the Condorcet paradox, the technical name of the situation I (almost) described.
Named after the Marquis de Condorcet (an 18th-century French nobleman who, Fisher writes, “had more fun with voting systems than most politicians”), the simplest Condorcet paradox occurs when there are three voters and three political parties A, B and C:
Voter 1 prefers A to B, but would rather have B than C
Voter 2 prefers B to C, but would rather have C than A
Voter 3 prefers C to A, but would rather have A than B

In these circumstances, no matter who is declared the winner, two-thirds of the electorate will have preferred someone else. There is no “Condorcet winner” – no party which, when compared to all others, is preferred by more people.

Source: Condorcet Paradox

1 comment:

Sackerson said...

And back in the real world, "the alternative vote" would make more people feel thay'd had some sort of say in their government. Especially if "none of the above" was an option, too.