When the City of New York hired William Bratton to be its next Police Commissioner, it wasn't a surprising decision. Bratton presided over a precipitous drop in violent crime when he was police commissioner in Los Angeles from 2002-2009. But is there another explanation for the drop in crime in Los Angeles during Bratton's tenure?
Kevin Drum, a blogger for Mother Jones who focuses on public policy and politics, has been a major proponent of an alternative theory for why the city has seen such a dramatic decrease in violent crime, particularly homicides. As Drum notes, communities all over the country have seen a similar drop in the same period, including New York, Boston and even cities with violent reputations such as Detroit. Obviously, Bratton can't be credited for those trends since he wasn't police commissioner in those areas too.
Drum and other writers have posited another cause: A steep decline in lead exposure among children. Childhood lead exposure peaked in the 60s and 70s, due to the fact that it was used in gasoline to prevent engine "knocking." Once it was determined that lead had disastrous effects on the mental development of children, leaded gasoline was phased out.
What does this have to do with the violent crime rate? Drum believes that the fact that the peak in crime rates (around the early 90s) came roughly 20 years after lead exposure reached its height in the early 70s isn't a coincidence. The theory, which is backed by pretty convincing evidence, is that violent crime rates hit their highs as the generation that was most affected by lead exposure came of age, and declined once those exposure amounts were mitigated.
This isn't to suggest that Bratton isn't qualified for the job. But it does indicate that conventional theories explaining the drop in crime – tougher policing, aggressive community engagement – may bear less responsibility than attempts to improve public health and green living ideas.