"Big-city homicides rose in 2015 and again in 2016, although not all cities experienced a large increase, and homicides fell in some cities. We consider two explanations of the homicide rise as guides for future research: (1) expansion in illicit drug markets brought about by the heroin and synthetic opioid epidemic and (2) widely referenced 'Ferguson effects' resulting in de-policing, compromised police legitimacy, or both. Larger increases in drug-related homicides than in other types of homicide provide preliminary evidence that expansions in illicit drug markets contributed to the overall homicide rise. The current drug epidemic is disproportionately concentrated in the white population, and homicides have increased among whites as well as among African-Americans and Hispanics. We surmise, therefore, that the drug epidemic may have had an especially strong influence on the rise in homicide rates among whites. Current evidence that links de-policing to the homicide rise is mixed at best. Surveys of police reveal widespread concerns about increased police-community tensions and reductions in proactive policing in the aftermath of widely publicized deadly encounters between the police and African-Americans. Increases in homicide followed decreases in arrests in Baltimore and Chicago, although it is not known whether the same was true in other cities. Nationwide, arrest-offense ratios and arrest clearance rates decreased in 2015, but they had been declining for several years when homicide rates were falling. The extent of de-policing and its possible connection to the recent homicide rise remain open research questions."
National Criminal Justice Reference Service [NCJRS]: http://www.ncjrs.gov/