i am only inspired to mention this because nate silver mentioned oddsmakers as evidence supporting his prediction. https://twitter.com/fivethirtyeight/status/

i am only inspired to mention this because nate silver mentioned oddsmakers as evidence supporting his prediction. https://twitter.com/fivethirtyeight/status/263948034105278464 https://twitter.com/fivethirtyeight/status/26394803410527846... i'm mixing examples here. intrade is a betting market, no line is set by a bookie - it measures public opinion. one way to look at it is that intrade is efficient and there was truly a "20% chance it will occur." the other way to look at it is "the odds were never 80/20" because most people betting on it were uninformed or misinformed (clearly watching WAY too much Fox news). this is unknowable, because it's not a repeatable event. prediction markets were originally based on the idea that folks with inside information would bet heavily and clearly justice roberts had other stuff to do. understanding how sports books work is not the same as saying "i know enough about sports to bet profitably." that said, bets set by a casino or sports book are different than intrade. a bookie is trying to maximize house profit, whereas intrade is pure sentiment. a sports spread can be -2 with 80% of people betting one side. the house might think the real spread is -4, and they expect the line to pay off. here's an example of how lopsided bets can be: http://www.thespread.com/ncaa-college-football-public-betting-chart#.UJWDjKg0V8E http://www.thespread.com/ncaa-college-football-public-bettin... I'm reading "sharp sports betting" by sanford wong right now. good quote: "I had the opportunity to ask Robert Walker, race and sportsbook director at MGM mirage, whether his company's action is balanced on football games...it appeared to me that sportsbooks might be taking lopsided action on about half of all NFL games. Mr Walker answered that what I hypothesized was indeed the case....then i asked him why he did not make more line moves to try and balance the action. his answer was that to move the line to try to balance the action would result in less profit for the sportsbook."