The Policy Wonk’s Guide to the Presidential Betting Market

This October, as the presidential election nears, we witness the strange intersection of the worlds of the gambler and the policy wonk. Daily, our best political observers reference the current prices of the presidential betting market. Unfortunately, I think their lack of knowledge of gambling mechanics leads them astray.

For starters, why do we care about what gamblers think about the election? The power of simple consensus estimates is remarkably powerful in a wide variety of settings (see James Surowieki’s The Wisdom of Crowds for examples). Each individual’s guess contains a kernel of truth and a lot of idiosyncratic error; when we average together individual guesses, the idiosyncratic errors filter out. Market prices are a much more powerful form of consensus estimate in which the more informed participants tend to be given much greater weight in the market. Indeed, a stronger condition holds: one perfectly informed individual can fully determine price.

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