Tensions always run high between sports fans of rival teams on game day. But a new study shows that the rise of legalized sports betting in the US is turning those tensions into something far darker.

In 2018, the United States Supreme Court struck down a federal law that blocked states from authorizing sports betting in a decision known as Murphy v. NCAA. Since that time, legalized sports betting has spread to 38 states plus Washington, D.C. and Puerto Rico. It has also raised a whopping US$9.3 billion for those states through taxation of those bets.

Now, a new study from Rice University says it has raised something else too: crime.

Using data from the FBI's Uniform Crime Reporting Program (UCR) and its National Incident-Based Reporting System (NIBRS), the Rice researchers examined crime statistics from 2017 to 2021. They then pulled the dates of professional sporting events across the country from Sports-Reference, an aggregator of sports data from all the major leagues, including the NFL, NBA, NHL, and MLB.

Next, they compared crime rates on the day before games and on game days themselves. For game-day activity, they looked at the period from the start of the event to four hours after its conclusion. They also split their data between years when sports betting was illegal and following its legalization on a state-by-state basis.

They found some sobering statistics.

According to the study, published in the Journal of Sports Economics, violent crime has risen by roughly 30-70% during games – from kickoff through four hours after they end – compared with the same time window before sports betting was legalized. Those crimes include assault, larceny, and vehicle theft, with assaults spiking between 60-90% and larceny increasing 30-100%.

The effects were most significant during home games and games with unexpected outcomes. In fact, assaults had the largest jump of all crimes – up to 93% – after a home-team upset. Games that were more stressful overall had a greater impact on crime rates.

"It is … worth noting that aggression may not stem solely from financial stress, as often observed in other forms of betting," said study co-author Wenche Wang. "We find recent evidence of increased crime associated with stressful games, such as those with close or tied scores throughout, as well as games that extend into overtime."

The researchers also found a slight "spillover" effect, with non-legal states bordering legal states also seeing a rise in game-day crime.

While those statistics might conjure up marauding bands of angry fans on big game days, it's important to note that the percentages translate to about 0.5 to 1.2 additional incidents per police agency per game window. Still, the researchers say their findings should be taken into consideration as states evaluate their legalized sports betting strategies.

"Sports gambling is exciting for fans and financially attractive for states, but our findings show it can also lead to more crime," said co-author Hua Gong, assistant professor of sport analytics at Rice University. "When people lose their bets or go through very stressful game moments, that emotional volatility can translate into aggressive behavior.

"Legal betting brings in revenue, but there are serious social consequences we cannot ignore. Lawmakers should consider safeguards, better consumer protections and public awareness efforts as the industry continues to expand."

Source: Rice University