The effect is exposure during childhood, so you can’t test for levels when they’re incarcerated as adults. But studies that have followed children who had high levels of exposure found they had higher crime-rates as adults.
And it’s not just correlation, there’s a lot of direct studies that link lead and aggressive behavior as well. Animals exposed to lead become more aggressive, lead has been directly show to effect neurotransmitters associated with impulse control, etc.
And the correlation really is overwelming. It’s been show to hold up across countries, and down to the neighborhood level (that is, children from neighborhoods with higher lead have a correspondingly high levels of crime then similar, close-by neighborhoods). Countries that phased out leaded gasoline more slowly saw slower declines in crime-rates.
I’ve become pretty convinced the lead-hypothesis is correct. There are multiple lines of evidence for it, and they’ve held up over years of study. And there isn’t any other explanation that correlates as well over such a wide range of geographic scales (from individuals to neighborhoods to cities and States to countries).
Acknowledging all the factors mentioned above and recognizing that how we accurately count crime is a complicated process, I think it’s worth mentioning that in the United States violent crime has been gradually increasing again while property crime is down.
There are some addition issues which haven’t been taken into account in this thread.
Our police are under a lot of pressure these days to keep the crime statistics low or lose their jobs. This is a good motivator to try a variety of solutions at the “in the trenches” level.
Many of our large cities are having budgeting problems and cutting some services has been seen as solution by some city management.
If police are overworked they often don’t get to a crime scene until after eyewitnesses may have given up and gone home. No police report = no crime committed.
There is pressure on the courts to lighten the load on our overcrowded jails. This can be demoralizing to the police force who risk their safety to secure a criminal only to see him on the street in a week. The implication with that is that some police may lessen their efforts after this happens repeatedly.
A police department can also lessen the amount of crime committed in the public’s eye by determining exactly how to charge out a crime. Disturbing the peace is an especially handy charge for hiding minor street violence.
And then there are those reports which just go missing.
Having worked closely with police in my job and having police as friends I’ve known about the politics of crime statistics for a long time so I was glad last year to see an article in “Mother Jones” which put it on the printed page.
Concerning neighborhood level results: keep in mind that the major driver for phasing out leaded gas wasn’t the issues with lead in the fuel itself, it was that cars with catalytic converters require unleaded gas. In the US, most cars after model year 1974 had to have them. What this means is that from 1974 until the final phase out in 1995, the amount of leaded gas that was sold in an area was pretty much proportional to the number of pre-1974 cars being driven in that area, which in turn is obviously related to income.
I suspect at least part of the international observations can be similarly explained. As emissions technology became more integrated into the 80’s and 90’s, most cars built in the US, Japan and Western Europe started to require unleaded gas even if they were sold in a country that didn’t require it. Switching from motorcycles, homegrown cars and older hand-me-down imports that burned leaded gas to newer imported cars that used unleaded gas would result in less leaded gas usage and is also a pretty good sign of a country with improving economic circumstances.
Most of the developing world has phased out leaded gas in the last 10 years or so, but for the most part that’s just facing the facts that the lead additive is hard to come by and even older hand-me-down cars require unleaded gas now. It’ll be interesting to see if the correlation continues to hold with them when the phase-out most likely has nothing to do with a political or economic shift.
What else has happened across the developed world in this time?
Well, there has been a big migration from labour being involved in manufacture and industry towards service businesses.
Maybe that lifestyle that consisted of bashing metal and tending noisy machines with weekends taken up with sporting confrontations, boozing and spousal abuse has been much reduced. Substituted by service businesses that rely on interpersonal skills. These days it is all email, meetings, call centres and media.
But you are ignoring that this lead-crime correlation seems to happen in every society studied. Yeah, you can offer some alternative correlations here, then choose another possible correlation over there, but lead-crime correlates everywhere.
The absolute number of 20-25 year olds has barely changed at all since 1980 (they’re a smaller chunk of the population, but not a smaller group in absolute terms). The absolute number of homicides has dropped by more then a third in the same period. It isn’t just that young people make up a smaller proportion of the population, young people are also committing fewer crimes.
The rise and fall of crime over the last few decades has been pretty carefully studied, without any widely accepted answers. You can pretty much assume any easy to check guess as to the cause, like simple shifts in demographics, has been examined and found not to be strong enough to account for the effect.
You’d think there would be an increase in crime involving youngsters as they are carrying expensive electrical goods nowadays that didn’t exist 20 years ago. Back in the day I certainly didn’t have anything worth stealing … including my homework.
I read an article on decreasing rates of pickpocketing that made the opposite point. People carry more expensive electronic goods, but a lot less cash then they used to. And while Iphones and the like are worth a lot on paper, actually fencing a stolen one is a non-trivial problem, while stolen cash is going to be worth its face value.
And since the major violent crime rate is down, cities have a lot more resources to go after petty theft, muggers and pick-pockets.
End result is that its a really tough time to be a pickpocket, and in a lot of cities the practice has almost vanished.
Is there some way to tell that adults were exposed to higher than normal levels of lead as children, and that’s why they become criminals (or is at least a factor)?
I doubt anyone would dispute that lead exposure causes bad things, including in some cases an increased propensity towards certain kinds of crime. I wondered if there was any way to tell who had become a criminal because of lead exposure, and who had much less exposure but stayed on the straight and narrow.
I don’t doubt this. Even if it is definitely established that lead exposure caused some crimes, all the other factors that lead to criminal behavior would still be in play, and might even drown out any other factor.
IOW it doesn’t have to be any one factor that caused the decline in crime. It might be decreased exposure to lead, as well as better police strategies, the aging of the population, a general increase in standards of living, abortion, etc.
I don’t think so (If there was, presumably that would be the study people would look at, instead of having to resort to studies that follow people from childhood). There are brain changes characteristic of lead exposure that can be detected in adults, but they aren’t unique enough to be directly traced back to lead exposure on an individual level.
No doubt. Also, just to be clear, “lead caused crime” is just shorthand for “lead caused the large increase in the crime rate that affected the industrialized world during the latter half of the 20th century”. Obviously crime pre-existed the use of leaded gasoline, and even if we get lead exposure down to zero, people will still be committing crimes.
The question is why the rate went up so fast, in so many places at the same time, and has dropped just as fast over the last two decades.
Sure, and certainly at least some of those things do cause a change in the base rate of crime (the aging of the population certainly does, even if its nowhere near large enough to explain the recent drop). But the crime wave was so large and so universal across such a wide variety of cities, states and countries that it seems likely that there was one root cause that drove it.
Problem is, in country after country in the deveoped world, the rise and fall of crime matches up to the environmental lead exposure. Regardless of variations in police strategies, abortion policies, standard of living changes, etc.
The matchup is too widespread to be explained by things that vary widely from country to country.