One possible cause of the 2020 murder increase: More guns

The year 2020 saw the largest recorded increase in homicides in United States history — an increase likely propelled by a complex mix of factors, from more guns to stresses of the pandemic to fewer police officers on the streets to a crisis in relations between police and citizens.

But one persistent theory is that a change in policing last summer primarily drove increased gun violence. This is an especially popular explanation among law enforcement figures. Former Baltimore Police Department Deputy Commissioner Jason Johnson recently argued that the real driver of last year’s murder rise was a severe decline in police activity, especially after protests erupted last summer in the wake of George Floyd’s murder.

St. Louis Police Commissioner John Hayden suggested that the police resources devoted to protests prevented officers from engaging in neighborhood policing. Former NYPD Commissioner Ray Kelly said police were “stretched to the limit” by the protests and coronavirus restrictions. Summarizing widespread reductions in stops and arrests, Johnson wrote that “when the Thin Blue Line retreats, violence charges in.”

But data from numerous large American cities complicates that narrative, suggesting that the change in policing alone is not sufficient to explain last year’s large increase in murder and that a growing number of firearms on the streets likely played a significant role.