So, Now I'm Thanking Richard Nixon and Pierre Elliot Trudeau ……… Odd History

It turns out that the surge, and subsequent drop, in crime in Canada also appears to be an artifact of lead exposure:

I'm happy to see lead at least get a shout out. Unless I've missed something, this might actually be the first time the New York Times has ever mentioned childhood lead exposure as a possible explanation for the decline in violent crime. Progress!

But while Eckholm is right to say that none of the other factors he mentions can explain a decline in violent crime that happened all over the world, he's wrong to include lead in that list. It's the one explanation that does have the potential to explain a worldwide drop in crime levels. In particular, the chart on the right shows the use of gasoline lead in Canada, which peaked in the mid-70s and then began dropping as catalytic converters became more common. Leaded gasoline was banned for good in 1990, and is now virtually gone with a few minor exceptions for specialized vehicles.

So what happened? As Zimring says, Canada saw a substantial decrease in violent crime that started about 20 years after lead emissions began to drop, which is exactly what you'd expect. I calculated the numbers for Canada's biggest cities back when I was researching my lead-crime piece, and crime was down from its peak values everywhere: 31 percent in Montreal, 36 percent in Edmonton, 40 percent in Toronto and Vancouver, and 53 percent in Ottawa. CompStat and broken windows and American drug laws can't explain that.

It is almost certain that lead exposure is a significant factor the rise and fall of crime world wide, and given the wide variations in techniques used by law enforcement, it is likely the most significant factor in the rise and fall of crime worldwide.

Given the clearly racist assumptions of broken windows policing, and the even more clearly racist subtext of America's fascination with incarceration, it's not surprising that the law enforcement establishment has studiously avoided looking at lead's effects on crime.

Racially biased law enforcement philosophies, particularly when it generates more money for law enforcement and incarceration is a feature of, and not a bug in, our society.