Thursday, May 05, 2005

Government: Duverger's Law

Pretty much every election cycle people complain about the two party system we have in this country. Luckily, no amount of complaining can overcome the power of math.

Virtually all of our elections are based on single member districts - one person per district per election - and it doesn't matter how much or how little you win by, if you have a plurality, you win. This is generally referred to as the first past the post system, which is a very poor horse racing metaphor that essentially means "winner take all." So if three candidates are running for Congress, and the Republicans get 41% and the Democrats get 40% and the Greens get 19%, the Republicans win, even though the center/left coalition of Dems and Greens are clearly in a majority.

This means that minor parties will almost always lose every election, because they will never be able to gain any post election power with an electorate that has two even moderately larger parties. And the most important thing about an election is that it determines who has power over the government (and thus also the economy, education, regulation, media, and everything else not limited by the Constitution and by the separation of powers) after the election. So people who want to accomplish any ideological or pragmatic goal rationally make the choice not to support minor parties.

It's not that the system is corrupt, or that people are stupid, or that there is something horribly wrong with the country. It's math.

This observation that winner take all elections naturally lead to stable two-party systems was first seriously written about by the French sociologist Maurice Duverger, in his appropriately named book, "Factors in a Two-Party and Multi-Party System." His observations have been so accurate, that people generally refer to them as Duverger's Law.


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