Do police deter crime?
A Florida State University law professor who studied the effects of an increased police presence during high terror alert in Washington, D.C., says they do. And not by just a little bit either.
Jonathan Klick, the Jeffrey A. Stoops Professor of Law at FSU, and Alexander Tabarrok of George Mason University, found a 15 percent reduction in crime in the police district where the White House and National Mall are located when additional officers were on duty during high terror alert days. The study was published in the Journal of Law and Economics.
The findings are significant because social scientists, lawmakers and others have long wondered whether spending more money on additional police is the answer to reducing crime. Klick and Tabarrok’s study suggests that it is.
"We found that the additional police had a pretty big effect on crime," Klick said. "Our local and federal governments spend tons of money on policing, and it looks like we may be justified in spending much more."
In fact, Klick, who in addition to his law degree has a doctorate in economics, goes as far as to say that doubling police forces—or at the very least increasing them by 25 percent—may be a good idea, although there may be a point of diminishing returns. Already more than $65 billion is spent annually on police in this country.
"We’re pretty confident that if we increase police forces by one-fourth, we would get our money’s worth," he said.
Although it seems obvious that more police should result in less crime, many previous studies have shown that isn’t the case—or worse, that more police actually equal more crime. It’s a puzzle that has been difficult to solve because cities with high crime rates have more officers. Do more police cause the higher crime rates, or do cities with high crime rates hire more police?
After the Office of Homeland Security implemented the terror alert system, Klick, who was working in Washington at the time, noticed police officers on every corner during high alert times—a reason that had nothing to do with the city’s crime rate. That gave him and Tabarrok the opportunity to conduct a so-called natural experiment to see the effect the increased police presence had.
They reviewed data between the day the alert system began, March 12, 2002, and July 30, 2003, a period in which the alert level rose and fell four times. The changes in the alert system proved to be important because the researchers were able to replicate the results each time the alert level was raised and reduce the possibility that the results were due to other factors.
They found a drop of about three crimes per day, or 15 percent, around the National Mall area where the increased police were concentrated during the high alert periods. Overall, crime was down in the city by an average of seven crimes a day or 6.6 percent, Klick said.
The reduction was mostly in the so-called street crimes—burglaries, stolen cars and the like. The increased police presence had no effect on murders and other crimes that typically take place out of sight.
More research is needed to see if the Washington, D.C., findings can be generalized to other cities, Klick said.