Tuesday, July 31, 2007

Research: NBA Scores Consistent with Occasional Point Shaving

With the NBA point shaving scandal front and center in the news, a senior thesis paper by Jonathan Gibbs of Stanford is getting a lot of attention. In his thesis, Gibbs found that the betting line does seem to have an effect on the final margin in games with large point spreads. And if you are going to fix a game, the easiest way to do it is to make sure the heavily favored team fails to beat a large spread.

Gibbs found that teams beat the Las Vegas sportsbooks' spread almost exactly fifty percent of the time over the 16,000 games in the study (7,802 compared to 7,855). But in the games where point shaving would seem to be most likely, where the spreads were 12.5 points or more, the betting lines were not accurate.

Gibbs and others have looked just at the games where point shaving would seem to be most likely -- the games with spreads of 12.5 points or more -- and a really weird thing became clear. Suddenly the betting lines were not accurate. Favorites fell way short of the spread at a normal rate, and beat it by a long shot at a normal rate. But if the score was close to the spread -- in short, if it was a game that would be easy to shave points in the final minutes -- then the favorite fell short of the spread more often than they beat it at a significant rate.

That means that if the spread closed at, say, 13, the favorite tended to win by something like 11 or 12 more often than they won by 14 or 15."