From Freakonomics this morning: Just how bad are football pundits at picking winners? Not bad – about half of the time right, against the spread. I’m not surprised that individuals picking can’t beat the Vegas line consistently – my understanding is that thos individuals who consistently make money on sports betting are doing it by taking advantage of those rare occasions when Vegas misses something, and are only betting on some very small minority of games.
But what kind of success could someone expect picking not against the spread, but just trying to pick a winner? Sean J. Taylor wrote something about this back in November in which he observed that “These rankings only are only about 70-75% accurate, while optimal ranking almost always breaks 80%.” By “optimal ranking” he means an ordering of the teams done retrospectively, at the end of the season; “these rankings” are various methods which attempt to assign a rating to each team based on its statistics and then picks the team with the higher rating to win the game. The disparity here is because the “optimal ranking” model is inherently overfitting.
As for rating systems, the simple rating system is an example, where the rating works out to be the amount that a team would beat an average opponent on on a neutral field. Interestingly, that rating system, as implemented at pro-football-reference.com, has the 49ers at 10.2 points better than an average team and the Ravens at 2.9 points better. But the 49ers are only a 4-point favorite today. I don’t really care about football so I’m not going to comment.
Also, I recently came across a series of articles from 2009 at Math Goes Pop! on the “Super Bowl Squares” betting pool: one, two, three. One interesting variant is to use the score mod 9 instead of the score mod 10 as the thing being bet on – due to football scores typically coming in sevens and threes, and the arithmetic fact 7+3 = 10, some last digits are far more common in football scores than others, but this effect goes away if you work mod 9.
And you guys know about Facebook’s football map (also by Sean J. Taylor!), right?
God plays dice 