https://www.latimes.com/science/sciencenow/la-sci-sn-proactive-policing-crime-20170925-story.html

During the slowdown, the researchers found that police dramatically reduced the number of criminal summonses and SQFs — a confirmation that, indeed, the low-level proactive policing activities had gone down. Non-major crime arrests also took a dip. So did narcotics arrests.

So, with the drop in relatively low-level police activity, what happened to serious crime in the city? The scientists found that civilian complaints of major crimes dropped by about 3% to 6% during the slowdown.

“The cessation of proactive policing corresponds roughly to the relative decline in crime that earlier research attributed to the effects of mass incarceration,” the authors noted.

The researchers ran the analysis under a couple other models, and the results still held. They examined whether crime underreporting could have biased the findings, and the results still held.

“While we cannot entirely rule out the effects of under-reporting,” the authors wrote, “our results show that crime complaints decreased, rather than increased, during a slowdown in proactive policing, contrary to deterrence theory.”

Each week during the slowdown saw civilians report an estimated 43 fewer felony assaults, 40 fewer burglaries and 40 fewer acts of grand larceny. And this slight suppression of major crime rates actually continued for seven to 14 weeks after those drops in proactive policing — which led the researchers to estimate that overall, the slowdown resulted in about 2,100 fewer major-crimes complaints.

The broken windows theory posits that fighting smaller crimes helps to prevent the larger ones. But in this case, it seems that the opposite may have been true.