Why has crime declined so much over the past 20 years?

Do you think it’s due to more indoor entertainment? Is it simply a correction back to normal from the unrest the social changes of the 60s created? Do you think it’s one of the controversial theories like lead removal or legal abortion? Is it simply because more people are in jail (this can’t explain the recent decline in Europe though)?

A case has been made several times on this board (and fairly convincingly as well) that regulations limiting or banning the use of lead has had a measurable effect on this. While I don’t think it’s completely proved, I’d say the evidence is compelling, and better than anything else I’ve seen.

Despite what some people some I believe their is more consumption per person globally than ever. In other words, in terms of resources, people are less poor due to technological advancement being able to produce food etc. much more efficiently.

Like a lot of things there are probably several answers which all contribute to different degrees.

There are multiple theories, some people, as XT said, like the “lead” theory. Other options are:

-We incarcerate so many people that we keep the criminals behind bars instead of on the streets.
-We have fewer people under 30. As the population, in general, ages, we are going to see a falloff because crimes, especially violent crimes, aren’t going to happen as often.
–Subsidiary theory: That abortion has cut the birth rate causing the above.
-Still another theory is that better and more aggressive policing, hence “more likely to be caught” is a significant deterrent.
-The spike from the 70s into the 90s was caused by crack, LSD, and/or other drugs.
-Gentrification has caused inner cities to become less prone to crime by introducing peace lovers and neighborhood cleaners to the urban centers.
-Less usable opportunity. In the 40’s and 50’s, after the WW2 left America an economic power house, people saw the opportunity to take things that they couldn’t otherwise get. Televisions, cars, jewelry, et cetera. After these things became ubiquitous, the crime rates fell.
-Someone once even told me that the fluoride in drinking water was making us all less aggressive.

All of these theories, including Lead, have their pros and cons and caveats. The biggest issue is that we have no idea why and all we have are general correlations to other trends that happened along side.

While we’re just talking the last 20 years, there are specific crimes that technology has helped greatly reduce.
For example, in the UK, car theft / joyriding was one of the most common crimes. Nowadays stealing most cars is such a PITA that few people try.
Now, maybe some of those potential car thieves will find some other crime to go and commit (e.g. burglary). But I think in a lot of cases it was just a crime of opportunity, and the opportunity has gone.

Is this trend documented outside of the US?

Yes, that’s one of the reasons its such a convincing theory. Almost all industrialized countries experienced a rise in crime around the same period, and all are now experiencing a decline. And differences in the timing of both the increases and declines correlate very closely to the relative timing of the introduction/elimination of leaded gasoline in that country. Countries which eliminated lead later also had a later drop in crime, and vice-versa.

And within countries, the correlation holds as well. Regions which eliminated lead first saw earlier declines in crime.

Its relatively easy to find other things that correlate with the drop in crime in one country, but its pretty hard to find something where the correlation holds across multiple countries.

And the reasons for thinking lead is a major factor in criminal behaviour goes beyond just a strong correlation with crime-rates. Lead exposure in childhood has been shown to have an effect on individuals future crime-rates, on violent behaviours in animal models, and shown directly to affect parts of the brain associated with IQ and impulse control.

Lead is by far the most convincing theory, IMHO. And its held up pretty well over a fairly long period of study (as opposed to say, legalized abortion, which seemed convincing at first, but hasn’t faired well in subsequent studies).

I hate to ask for a link – but is this just a correlation?

Or was there some reasoning to suggest causation?

Because living in a poor country increases penis size, a pirate shortage caused global warming, and ice cream consumption leads to murder.

Most of those things aren’t correlations. A correlation is a mathematical relationship between two quantities, not just a vague “one thing goes up as another thing goes up”. Look at the X-axis of the pirate graph, you’d be pretty hard pressed to find an actual mathematical function that takes you from one to another.

And even if they did correlate, the things in those graphs are only one instance of each correlation. The lead/crime correlation holds across a huge number of cases, from the level of nations to that of neighborhoods.

“Correlation doesn’t prove causation” was originally a useful warning against ignoring the possibility of confounding variables. But its become a sort of anti-science buzz word, a lazy way to handwave away any study. A strong correlation does in fact, prove two things are casually linked, either directly to each other or each to a third variable.

(and to answer your actual question, see my original post, there are reasons beyond correlation that support the lead hypothesis).

It’s all of the above. The world is a complicated place, no single factor caused the rate of violent crime to rise in the first place, no single factor caused it’s decline. The only thing you can count on is that someone claiming there was a single dominant cause for the increase or the decrease is wrong.

I suggest checking out the thread we had about the topic some time ago. There you’ll find quite a few arguments and statistics for/against the lead theory.

Many different reasons. I would never underestimate a correlation between the number of young adults in a society and the crime rate. Now, this is not to say all teenagers are criminals. However, younger male adults do have a propensity for criminal activity in comparison to those in the age range of say 40 to 50 years of age. I dont think it a coincidence that the decline in birth rate around the late 1960’s into the early 1970’s in both the US and UK resulted in a falling crime rates in both countries from the 1990’s onwards.

It’s not “some people like the lead theory.” It’s “the lead theory has much stronger evidence supporting it than other theories.”

The theory that access to porn via the Internet decreases rape also seems to have some very strong evidence.

I disagree. Individual crimes are obviously complicated things with many causes. But the big increase, and then drop, in crime in the late 20th century was such a wide-spread phenomenon, was so similar across such a wide swath of countries and smaller geographic regions and was so large, that I think its unlikely to have been due to some large number of smaller factors. To the first order, anyways, a single cause seems far more probable.

The crime rate just amongst young males went up, and then down as part of the crime wave, so their increasing or decreasing proportion in the population doesn’t explain the phenomenon.

(I always kind of wonder why people bring up this theory, simply because its both so obvious and so easy to check, that there wouldn’t really be any mystery to solve if it were the explanation. The fact that people are still debating what caused the increase and then drop in crime twenty years on is a pretty clear check that it can’t be explained by some simple shift in demo-graphics).

You have the right to be wrong. Look at the list of factors mentioned here already and tell us which ones are insignificant in the change.

I think it’s harder to get away with a crime now and even the poor live relatively comfortable lives such that the risk of committing crime is not worth it.

Also, it’s not because the US locks up every young black male for bullshit reasons (War on Drugs). The trend of falling crime rates is happening globally so please don’t try and justify that nonsensical agenda.


You mean it doesnt explain the entire phenomenon. Everything else being equal it is a major influence on crime rates. Which is why I said I would never underestimate a correlation not that it was the only factor.

Your point about the reasons for crime rate decline still being debated today are interesting. Again, dont underestimate vested interest here. Many social scientists/workers and criminologists have a vested interest in it not being a birth rate linked model. Or of at least minimizing such an explanation.

Most of them, simply because the crime-wave happened in places that included them and places that didn’t.

That doesn’t mean these things have no effect on crime. But they’re obviously being swamped by whatever factor caused the large-scale change.

The demographic explanation is a good example. The idea is that young men commit crimes at a higher rate then other people, so the demographic shift to an older population caused the decrease in crime. And to an extent, that’s certainly true, young men do commit crimes at a much higher rate then their peers. All other things being equal, a larger proportion of young men in a population does correlate to having a higher crime rate.

But in the US, the crime rate peaked in the early 90’s, and then fell for the rest of the decade, even in places where the population of young people was still increasing. Its a near-certainty the increasing number of young people was causing more crimes to be commited, but the effect was swamped out by whatever caused the general decline. So everywhere saw a net-drop.

Obviously lead isn’t the sole cause of crime. If we had zero lead, there would still be crime, and other factors would cause it to go up and down. But I think the case is very strong that lead is the sole cause of the crime wave that took place in the last half of the 20th century.