Policing Algorithm To Reduce Crime

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Can math help keep our streets safer? A new study by a UCLA-led team of scholars and law enforcement officials suggests the answer is yes.

A new study by a UCLA-led team of scholars and law enforcement officials suggests the answer is yes. A mathematical model they devised to guide where the Los Angeles Police Department should deploy officers, led to substantially lower crime rates during a recent 21-month period. “Not only did the model predict twice as much crime as trained crime analysts predicted, but it also prevented twice as much crime,” said Jeffrey Brantingham, a UCLA professor of anthropology and senior author of the study.

How long did it take them to develop something so sophisticated, you ask? Six years of mathematical research and a decade of police crime data were needed to develop this model. The program predicts times and places that serious crimes will occur based on historical crime data in a given area. A key to its success, Brantingham said, is that the algorithm behind the model effectively “learns” over time, much the same way that your video streaming service knows what movie you’re going to watch tomorrow, even if your tastes have changed.

Beginning in 2011, the researchers analyzed crime trends in the LAPD’s Southwest division and in two Kent divisions to determine whether their model could predict, in real time, when and where major crimes would occur. Their analysis in Los Angeles focused on burglaries, theft from cars and theft of cars. In Kent, they studied patterns for those crimes as well as violent crimes including assault and robbery.

The researchers tested the computer model by pitting it against professional crime analysts, seeing which could more accurately predict where crimes would occur. The results were staggering. In Los Angeles, the mathematical model correctly predicted the locations of crimes on 4.7 percent of its forecasts, while the human analysts were correct just 2.1 percent of the time.

Based on those results, the researchers estimated that using the algorithm would save $9 million per year in Los Angeles, taking into account costs to victims, the courts and society. Brantingham said the mathematical model’s success rate could be improved even further, but emphasized that it cannot replace the police force. Rather,  it’s intended to help police officers do their jobs better.

“We’re not trying to explain everything,” he said. “But there are many aspects of human behavior that we can understand mathematically.”

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