Why did crime fall in the 1990s? A NY Times article suggests an answer:
The answer, according to Jessica Wolpaw Reyes, an economist at Amherst College, lies in the cleanup of a toxic chemical that affected nearly everyone in the United States for most of the last century. After moving out of an old townhouse in Boston when her first child was born in 2000, Reyes started looking into the effects of lead poisoning. She learned that even low levels of lead can cause brain damage that makes children less intelligent and, in some cases, more impulsive and aggressive. She also discovered that the main source of lead in the air and water had not been paint but rather leaded gasoline — until it was phased out in the 1970s and ’80s by the Clean Air Act, which took blood levels of lead for all Americans down to a fraction of what they had been. “Putting the two together,” she says, “it seemed that this big change in people’s exposure to lead might have led to some big changes in behavior.”
It sounds like a liberal idea, blaming crime on pollution, which is caused by evil capitalist behavior.
But underlying the idea is another idea that drives liberals crazy with anger; that people can have a biological disposition to being criminal. Ms. Reyes says lead makes children "less intelligent" (liberals only think intelligence is important when we can blame evil corporations) and "more impulsive and aggressive." We know that these personality traits are also genetic. Therefore, this is an admission that some people are born more criminal-prone than others.