Tuesday, June 24, 2008

The Crooked NBA

I always believed that the NBA was rigged (which was confirmed in my mind in the 2001 Eastern Conference Finals in which the refs basically handed the series to the Philadelphia 76ers). However, I have always referred to this belief publicly as "my one crackpot theory." Then it was revealed that an NBA ref was in debt to the mob, fixed a bunch of games, and knows about a playoff series that was rigged last year.

I now refer to my theory as "my prescient theory that is obviously true."

Anyway, since the Tim Donaghy story broke last year economists have taken up the task trying to locate anything out of the ordinary about how games are called. The most recent study was done by Kevin Hassett of the American Enterprise Institute. He found that:

Since the 2002 regular season, home teams won a little more than 60 percent of the time. In the playoffs, when a series might be extended by referees favoring the home team, the winning percentage skyrockets.

If the true odds of the home team winning were six in 10, as in the regular season, then the odds of observing 34 home victories in 42 games simply by chance are close to zero.

As may have been evident in the NBA Finals, home teams tend to get more calls. This would affect the outcome because foul calls lead to free throws; what's more, the home team can play more aggressive defense once it's aware that the officials are being kind to them.


He believes that refs intentionally try to extend playoff series. If all home games are won by the home team, the series will go 7 games. But what happens if a visiting team is on the brink of elimination?

Later in the series, a home victory might be necessary for the games to be extended. In that case, the officiating bias might be greater. Sometimes a series might end before seven games if the home team wins. In those cases, the favoritism may be less. In the seventh game, the bias might disappear, as it no longer would serve any purpose. The series will end no matter what.

First let's look at Game 5. In the 2007 and 2008 playoffs, 25 series extended to at least five games. At times when the home team was leading three games to one, and another win meant the end of the series, the visiting team shot 1.1 percentage points better than the home team. When a home-team win doesn't end the series, the home team's field-goal percentage is 5.4 points higher on average than the away team's.

Let's turn to Game 6: In the 2007 and 2008 playoffs, in games where the home team was behind in the series, it was called for 4.1 fewer fouls on average than the away team.


And what about in "Game 7" where no further extension of the series is possible? If the refs are motivated by extending the series to make the NBA more money, you would expect game 7 to see none of the shenanigans listed above. And...

In the seventh game the foul differential drops to just one during the past two years. That's little more than the regular season average.

All the data suggest there have been movements in the number of calls that are consistent with the suspicion that the NBA sought to extend series.


Read the whole thing. Here is more.

Hat tip to Marginal Revolution, where Tyler Cowen points out that:

Note that fouls called on a team are often a measure of how tired that team is or how sloppy it is on defense. So if teams play better with their back to the wall, at home, or if stamina matters more toward the end of the year, these correlations could potentially arise through natural means.


Oh, and don't forget that in addition to being crooked, mob-indentured idiots, NBA refs also appear to be racists.

Ah, the NBA. Where Rigging Games Happens!

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