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Researchers dispute study pointing
to college basketball point shaving
Bernhardt, professor of economics
Reutter, Business & Law Editor
photo to enlarge
by L. Brian Stauffer
Dan Bernhardt and University of Maryland co-researcher
Steven Heston dispute a widely
publicized academic study that claimed to find
statistical evidence of point shaving among college
basketball teams that are strongly favored by
Las Vegas bookmakers.
A University of Illinois economist disputes a widely publicized academic
study that claimed to find statistical evidence of point shaving among
college basketball teams that are strongly favored by Las Vegas bookmakers.
Dan Bernhardt, an Illinois professor of economics,
and co-researcher Steven Heston, a professor of finance at the University
of Maryland, conclude that the statistical anomalies identified by the
previous study “are intrinsic to the game itself and are not indicative
of an epidemic of gambling-related corruption” in college basketball.
Point shaving is the practice by a favored team of winning games by
less than the bookmakers’ point spread in order to yield profits
for gamblers who bet on the underdog. Because bets are based on the
margin of victory rather than on wins and losses, players can cheat
by missing a basket or two and still win the game.
Justin Wolfers, an economist at the University of Pennsylvania, received
widespread media attention last spring when his “Point Shaving:
Corruption in College Baseball” appeared in the American Economic
Using a sample of 44,120 NCAA Division I basketball games between 1989
and 2005, Wolfers documented that a team favored by 14 points was about
6 percent more likely to win by fewer points than to win by more points.
Wolfers concluded that strong teams missed the spread too often to be
accounted for by chance.
“This finding, if correct, would mean either that the very best
NCAA teams shaved points, for they comprised the bulk of the strong
favorites, or else that a really high percentage of college players
occasionally engaged in criminal activity by missing a basket or two
to blow the spread without blowing the game,” Bernhardt said in
“Either possibility,” the Illinois economist added, “would
indicate remarkable levels of criminal activity and would call for radical
policy reform and policing in college sports.”
Bernhardt and Heston, however, wondered whether the patterns discovered
by Wolfers were due to player corruption or the nature of the game itself.
To answer this question, the researchers used two approaches. First,
they looked at the changes in the point spread between the opening and
closing lines, which was not done in the Wolfers study. The opening
line is the point spread that bookmakers initially quote, and the closing
line is the spread quoted just before the game begins.
They identified 4,350 games in which the closing spread was wider than
the open spread, and 4,956 games in which the spread either remained
unchanged or fell.
Their hypothesis was that if the opening line on a favorite team increased
between the opening and closing spreads, more money was being bet on
the favorite than the underdog, making point shaving implausible. On
the other hand, in games where the spread fell between the opening and
closing lines, then gamblers betting on the underdog may have induced
members of the favored team to intentionally play badly in order to
win by less than the spread.
Finding very similar patterns regardless of whether the point spread
rose or fell, the researchers report no statistically significant evidence
of point shaving.
But this still left open the possibility that gamblers bet on small
scales that did not move the lines or that they simply spread their
bets out cleverly enough so that the lines did not move.
To examine these possibilities, Bernhardt and Heston investigated games
among non-elite Division I teams for which Las Vegas bookmakers set
no betting lines because the games drew almost no recreational wagering.
In place of the point spread, the researchers used the differences in
Sagarin ratings of team strength adjusted for home court advantage to
construct a measure of the amount by which one team should be favored.
“We compared the frequency by which teams won by a little less
than this estimate versus the frequency with which they beat the estimate
by a little, and again we found that they won more often by a little
less than by a little more,” Bernhardt said.
“In other words, the statistical properties that Wolfers identified
in his paper seem to be intrinsic to the game of basketball itself,
occurring independently of whether there are incentives to point shave,
and are not indicative of an epidemic of gambling-related corruption.”
What then caused the “asymmetry” in winning margins detected
Bernhardt and Heston offered two reasons in their working paper:
• Teams ahead by a small margin hold the ball at the end of a
game, strategically reducing the number of scoring opportunities for
both teams in order to maximize the probability of winning. “This
strategy has the effect of reducing the chances of beating a large spread,”
they noted. “In contrast, a team up by a large margin is sure
to win and will not hold the ball, thus raising the frequency of blow
• The impact of foul troubles on strong and weak teams is likely
to have a different impact on the final score. “Strong teams tend
to be deeper, with a stronger bench, so if the top players get in foul
trouble, the team is still likely to win by a small margin,” Bernhardt
said. “But the same it not true for a weak team. If a weak team
gets in foul trouble, it is likely to get blown out because its secondary
players are weak.”
Combining these two observations, the researchers believe that a strong
team is more likely to win by a little less than the spread than by
a little more than the spread.
Their working paper, “No Foul Play: Honesty in College Basketball,”
can be accessed online in pdf form.