VOX: From 2014 to 2019, Campbell tracked more than 1,600 BLM protests across the country, largely in bigger cities, with nearly 350,000 protesters. His main finding is a 15 to 20 percent reduction in lethal use of force by police officers — roughly 300 fewer police homicides — in census places that saw BLM protests.
Campbell’s research also indicates that these protests correlate with a 10 percent increase in murders in the areas that saw BLM protests. That means from 2014 to 2019, there were somewhere between 1,000 and 6,000 more homicides than would have been expected if places with protests were on the same trend as places that did not have protests. Campbell’s research does not include the effects of last summer’s historic wave of protests because researchers do not yet have all the relevant data.
…One other possible explanation for the increased murder rate is that law enforcement officials are the ones voluntarily reducing their interactions with the community and as a result emboldening criminal activity. One way to observe whether police are reducing their efforts is to see whether the share of property crimes cleared falls over this period. In other words, are police not trying as hard — either because they are demoralized or angry at public scrutiny of their behavior — to solve low-level crimes that are reported to them? Campbell observes a 5.5 percent decline in the share of property crimes cleared, which is consistent with police reducing their efforts immediately following the protests.