https://www.city-journal.org/new-evidence-connects-police-protests-and-rising-violent-crime
In 2015 and 2016, the coincidence of a major surge in homicides following mass protests over the police killing of Michael Brown in Ferguson, Missouri, prompted a heated debate about whether the demonstrations, and the anti-police hostility they engendered, helped cause the murder spike. Law enforcement leaders and some public commentators—including City Journal contributing editor Heather Mac Donald—identified a “Ferguson Effect,” whereby public scrutiny reduced police proactivity and led to an increase in violent crime. Supporters of the protests just as fervently derided the idea as imaginary and “debunked.”
Social scientists made a few contributions to this debate, but the research they produced offered limited insight into the causal relationship between scrutiny, proactivity, and crime. Two new studies, however, rely on better data sets and methods to provide strong evidence that highly scrutinized officer-involved fatalities reduce discretionary police activity and lead to an increase in violent crime.
The more-recent study, just published in the Journal of Public Economics by university economists Cheng Cheng and Wei Long, looks at the effect of Brown’s death on police activity and crime on a week-to-week level in St. Louis (which is near Ferguson), and on a month-to-month level in 60 big cities. The St. Louis police department collects high-quality data on self-initiated activity, the authors note, allowing them to assess in specific detail police behavior just before and just after Brown’s death.
Their findings manage somehow to be both unsurprising and shocking. In the immediate aftermath of Brown’s death, self-initiated arrests fell 62 percent. Similar declines are seen across nine out of 11 categories of self-initiated activities, including foot patrol (down 82 percent) and pedestrian checks (76 percent). Notably, the decline in arrests is concentrated among misdemeanor arrests (more discretionary than felonies) and among arrests of blacks (rather than whites). This reduction in police activity persisted for at least the next two years. In the same period, the city experienced a significant rise in homicide and aggravated assault.