Who would have guessed getting the lead out would reduce crime?

Over the past few years when crime statistics have come out, they have generally been lower than the year before. It's a curious trend.  Why as the world gains population, cities grow more crowded and the income gap grows, even during the worldwide economic collapse a few years ago, do crime statistics show a downward trend? It's a curious situation to which no one has been able to find an answer. The trend defies the general understanding. By all counts the rate of crime should be increasing.

R.  Nevin via the BBC

Now someone has come along with a surprisingly plausible explanation.  Researchers on both sides of the Atlantic Ocean have made a logical connection between lead in gasoline and crime. According to their research, 20 years after lead was first added to gasoline, crime increased at a comparative rate. Then, 20 years after producers removed lead from gasoline in the 1970s, the crime rate worldwide began dropping accordingly.

Lead has been blamed for many maladies in humans, and the researchers point to the fact that lead in the atmosphere reduces a brain's gray matter with resultant effects on behaviors such as impulse control. According to their logic those effects lead to more crimes. Other scientists disagree with that theory, questioning whether biology can be linked to crime.

Still, the research shows a remarkable parallel between the addition and reduction of lead in gasoline and crime and perhaps suggests at least part of the reason why against social odds, the rate of crime keeps dropping.

Here's the full story from the BBC