I just had a look at 538 and I'd defintely put my money with betfair or intrade. There is no accounting for things like the 'Bradley effect' or other highly cor

I just had a look at 538 and I'd defintely put my money with betfair or intrade. There is no accounting for things like the 'Bradley effect' or other highly correlated events on 538. I'm sure many bettors do use it as a resource but their judgement is likely to be a lot more subtle and incorporate more factors than the statistical analyses provided by the site. Kind of like the way that humans are still smarter than artificial intelligence (which is currently much like statistical techniques). > If I was placing any bet Well you should make a fair bit of money if 538 is accurate. Betfair has had 50K available right now for Obama at 1.08 implying a 92.5% chance which looks pretty good considering 538 says it is 98.1%. If you bet 50K you'd have a probabilistic profit of nearly 3 grand (50K * 1.08 * 98.1%). But when you actually went to put the cold hard cash down I'm sure you would have some second thoughts about 538's models. The whole point of betting markets is that talk is cheap. > There's no empirical test of likeliness Yes that is a problem. If betfair was (accurately) pricing in a 10% chance of a significant, accoss-the-board Bradley effect then there would be a 90% chance it would not occur and 538's results would look more accurate (across the electorates). However that 10% chance (if accurate) would be enough to make betting according to betfair's odds profitable vs 538's odds. In general this is reflective of the 'Black Swan' problem of uncommon events such as a market crashes. Those that underestimate the risk can often make money for long periods of time by betting against it. But when the risk event strikes all those profits and more can be wiped out.