Basketball Statistics Blog

Friday Press Clippings:
Point Shaving in NCAA Basketball: Corrupt Behavior or Statistical Artifact?

From Temple University
By George Diemer and Mike Leeds
Download source here: ' Point Shaving in NCAA Basketball:
Corrupt Behavior or Statistical Artifact? ' by George Diemer and Mike Leeds

"... Gambling on sporting events has probably existed as long as sports themselves. The founding myth of the ancient Olympic Games surrounds a chariot race that the Greek hero Pelops rigs so as to win the race and marry the king’s daughter.

Now, as then, gamblers have an incentive to insure that they win their bets on athletic events by somehow fixing the outcome. ..."

"... Point shaving typically occurs when one or more participants ensure that his team wins by less than the point spread.1 The point spread is the number of points by which gambling houses expect the favored team to beat the underdog.

Point spreads are a popular form of gambling because they attract bets on games between two unevenly matched teams. A team can lose the game badly, but it can still garner support by gamblers if they can bet that the team will lose by less than the bookmakers predict. ..."

"... The nature of basketball lends itself to point shaving. Basketball is a much higherscoring game than sports like soccer or baseball. As a result, the final point differential is generally much larger in basketball.

The wider differential increases the opportunity for allowing the other team to score or to failing to score oneself without greatly increasing the chance that one will lose the game.3 In addition, unlike football, relatively few points can be scored in any one possession, which limits the ability of a team to make up a large deficit very quickly.

Finally, the large number of regular season games reduces the amount of scrutiny any one game receives. ..."

"... As noted above, point shaving is more likely to occur at higher point spreads. As
the spread increases, it becomes easier for players to satisfy their secondary objective
(winning the wager) without compromising their presumed primary objective (winning
the game). ... "

"... If the evidence of point shaving is a statistical artifact, then regular season games and tournament games should show similar results. Under the null of no point shaving, we would again expect to find heteroskedasticity for post-season games.

If we cannot reject the hypothesis of a constant variance, then we have still more reason to believe that incentives to shave points again effect game outcomes. This time, as the incentives to shave points decreases in tournament play, statistical evidence of point shaving (heteroskedasticity) disappears. ..."

"... We show that point shaving is more likely to occur for regular season games that
have larger point spreads. This satisfies the gamblers who want to fix the game while
minimizing the change that the favored team will lose the game.

Because post-season games receive much closer scrutiny than regular season games, they are likely to be much harder to fix undetected.

Moreover, because post-season games are much more important than typical regular season games, we expect players to be more reluctant to participate in point shaving. Our results confirm this hypothesis.

Our results thus reject the null hypothesis of no point shaving when the incentives to shave points are strong and fail to reject the null hypothesis when the incentives are weak. ..."

Read more articles in Temple University.

To read today's 'Press Clippings' in Spanish, click this week above on the 'Español' tab or afterwards click here: ' El Uso de Indicadores de Desempeño
Normalizados para la Valoración de Jugadores: el Caso de las Estadísticas por Minuto en Baloncesto ' by J. A. Martínez, and L. Martínez .

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