Tuesday, March 04, 2008

Causation

Correlation is not causation. Paul Cassell at the Volokh Conspiracy asks whether more prisons have been accompanied by less crime, in response to the recent Pew Center on the States study showing that 1 in 100 persons in the US is in jail or prison.

The Pew Center claims that we are not really getting anything in return for the moneys spent on prisons. But curiously, despite the claim that this expenditure is "failing to have a clear impact either on recidivism or overall crime," the study never attempts to assess the impact on overall crime.

As a quick way of assessing the return is interesting to compare the moneys spent on prisons over the last twenty years(collected in the Pew report) and crime rates over the same period of time.


[See chart at link.]

As can be seen, significant increases in spending on prisons has coincided with significant reductions in crime. Of course, proving causality would require a more sophisticated analysis. But it would be remarkable to think that the prison growth has had nothing to do with the fact that violent crime rates have reached their lowest point in recent years, according to the Dept. of Justice Bureau of Justice Statistics. [internal links omitted]

I'm amazed that there are "significant reductions in crime" considering how many things we've made crimes that were not so when I was a child. On the other hand, the comments tell some interesting tales. One commenter asserts that there is a study saying that if you look at the number of institutionalized mentally ill people and the number of imprisoned people, the total is the same (as before the great de-institutionalizing movement of my youth) but the proportions have roughly reversed, and wonders how it helps the mentally ill to be imprisoned instead of institutionalized; in response another commenter writes:

It doesn't help the mentally ill. To the extent that it reduces violent crimes committed by the mentally ill, it helps society. It is a very clumsy and crude "solution," however. The decision to deinstitutionalize the mentally ill meant that people who in 1960 might have been institutionalized before they got around to murder, rape, kidnapping, or mayhem, now have to pretty near kill someone before they get any attention.

Los Angeles County Jail has effectively the largest mental hospital in the country now because of the decision to largely destroy the public mental hospital system, starting with the Community Mental Health Centers Act of 1963.


Another commenter compares our prison rate unfavorably to China's, but is rebutted by a response that points out China's death penalty numbers and suggests that if we killed 8,000 convicted criminals per year we might well have more people afraid of being caught and therefore deterred from crime.

I am drawn to the intuitive (but not necessarily empirical) truth of the age theory of crime (that is, most crime is committed by men from the age of puberty through about age 30), and a commenter makes that point, too:
I am a career prosecutor (and have handled death penalty cases both in my state Supreme Court and the 9th Circuit, so I am no soft-on-crime liberal).

That said, I agree with Public Defender. We are going from the "baby boom" to the "baby bust"--and I believe there is a strong corrolation between an aging population and a drop in crime.

I remember my very wise Criminal Procedure professor (who moonlighted as a Federal Magistrate Judge) saying, "The greatest indicator of recidivism is age."

What he meant, and which I have observed over the years to be true, is that if you walk into an average state courtroom on arraignment day, most of the defendants are under 30. If you see a 40-something charged with burglary or robbery or drug offenses, you can almost guarantee that person is in not in court on their first offense.

[...]
[T]here is a sharp drop-off between 20-somethings commiting crimes and 30-somethings committing crimes. It is as if a lightbulb goes off in many criminals' heads around the age of 30 and they think:

"This is really stupid. I don't like having people watch me take showers and tell me what to do 24/7. Prison and jail sucks."


I don't have a conclusion here, just lots of ruminating over this rich and varied thinking meat.

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