Even as the demonstrations abated, what is commonly called “proactive” policing declined. Police department data show that street and vehicle stops in Minneapolis and Philadelphia dropped sharply in June. In Chicago and New York, arrests declined steeply. And in cities around the country, both law-enforcement and citizen reports suggest a general reluctance by officers to engage in hot-spot and other enforcement efforts that are most effective in deterring gun violence.

The idea that reductions in policing might be leading to more shootings has historical precedent. Heather Mac Donaldproposed a “Ferguson Effect” in May 2015 to explain homicide increases in the aftermath of antipolice protests following Michael Brown’s death in Ferguson, Mo., the previous year. Similarly, my research with Richard Fowles identified declines in police street stops as the triggering event for the 2016 homicide spike in Chicago. Beginning in late 2015, pursuant to an agreement with the American Civil Liberties Union, Chicago police significantly reduced stop-and-frisks in the city. The result was a deadly homicide spike the following year.

The pattern in Chicago in 2016—a dramatic spike in shootings and homicides but not other crimes—is the pattern in many cities across America today. What Chicago suffered in 2016 is playing out across a much larger stage today—a new and deadly “Minneapolis Effect.”