Thursday, September 28, 2017

Will Releasing Convicts from Prison Increase Crime?

The Open Philanthropy Project has long been interested in the effects of America's mass incarceration. Now that the tide seems to be turning in their favor, they decided to commission a major study of whether reducing the prison population might lead to a major increase in crime. The study was carried out by David Roodman. He calls his project a "mass replication" of the best available studies on prison and crime, meaning that he went very thoroughly back through the data used in these studies, checked all their math, and asked the original investigators pressing questions about decisions they made. (Why did you look at this variable rather than that one? Why did you use this data set rather than some other?)

Alex Tabarrok is one of the study authors that Roodman put through this process, and Roodman ended up concluding the opposite of what Tabarrok's paper argued. But Tabarrok was nonetheless very impressed by Roodman's diligence:
My paper on Three Strikes with Eric Helland was one of the papers that Roodman replicated. (Fortunately, it did replicate with the exception of one error in a table.) I can vouch that Roodman gave us tougher scrutiny than did the peer reviewers.

Not surprisingly, I don’t agree with all of Roodman’s conclusions but rather than pushing back I think it more important to underline how impressive the replication project is. There are many review papers in economics but a replication project of this magnitude is nearly unprecedented. In our paper on the National Science Foundation, Tyler Cowen and I advised the NSF to put more efforts into replication. We wrote:

The NSF could support replication studies on a significant scale. A significant fraction of economic research does not easily replicate…Replication and reproducibility studies are true public goods that are not rewarded highly by most top journals or by the tenure process at research universities.

Roodman and OPP have demonstrated the value of replication on a large scale.
And what did Roodman find?
I estimate, that at typical policy margins in the United States today, decarceration has zero net impact on crime. That estimate is uncertain, but at least as much evidence suggests that decarceration reduces crime as increases it. The crux of the matter is that tougher sentences hardly deter crime, and that while imprisoning people temporarily stops them from committing crime outside prison walls, it also tends to increase their criminality after release. As a result, “tough-on-crime” initiatives can reduce crime in the short run but cause offsetting harm in the long run. Empirical social science research—or at least non-experimental social science research—should not be taken at face value. Among three dozen studies I reviewed, I obtained or reconstructed the data and code for eight. Replication and reanalysis revealed significant methodological concerns in seven and led to major reinterpretations of four.
Note one key detail about what Roodman says above: "at typical policy margins." He is not saying that freeing all prisoners would have no significant effect on crime, only that the kind of sentencing reform efforts now under way have no significant effect. So it might be that if we ratcheted the prison population down to its size in 1980, when it was less than half what it is now, something bad might happen. But the sort of 5 to 20 percent reductions states like Georgia are seeking do not seem to lead to crime waves.

I'm not going to tell you that Roodman is right; these are very hard problems, and studies have come to varying conclusions. But as I have said before in similar cases, when researchers can't even agree on the direction of an effect, some finding it negative and some positive, it is not likely to be very big. Cutting our prison population in the way reformers are actually seeking would likely not lead to major crime problems, and it might have good effects in the black and Hispanic communities from which so many prisoners come.


G. Verloren said...

Are these people looking at the European prison systems? Because it seems striking that so many wealthy developed countries have so much less crime than we do while also being far less prone to incarcerating people who commit crimes.

I mean, just as a single example, let's look at Scandinavia. Per 100,000 people about 57 are incarcerated in Sweden, about 67 in Denmark, about 75 in Norway, and about 55 in Finland. But here in the US, we incarcerate about 698 people out of every 100,000! That's ten times the incarceration rate of any of them!

So what are these countries doing differently?

Well, for one thing, they pay much higher taxes than we do. You might think that taxing people more heavily would lead to more crime - and you'd be right, if you simply took that money away and didn't reinvest it in society. But in places like Scandinavia, the high taxes serve to promote social welfare, assisting and protecting the most vulnerable portions of the population, and raising quality of life for everyone.

Happy, healthy, educated, and empowered people overwhelmingly don't commit crime. Miserable, unwell, ignorant, and desperate people do.

Unknown said...

"while imprisoning people temporarily stops them from committing crime outside prison walls, it also tends to increase their criminality after release": doesn't this suggest that, while we should reduce the numbers that we put in prison in the future, those who are in prison now should be kept there? I'm not actually suggesting this, but if we take these studies seriously, isn't that one conclusion?

G. Verloren said...


It really breaks down into what you view the purpose of incarceration to be.

If you think incarceration is simply about removing criminals from society and perhaps also about inflicting punishment and vengeance on transgressors, then yes, locking them up forever ensures they don't commit more crimes, and that they continue to be punished in perpetuity.

But if you think incarceration is about rehabilitation, then you want to keep them locked up for as short a time as possible, because the longer they're removed from society, the harder it becomes for them to reintegrate into it later on.

And if you also think incarceration should be cost effective, and not impose a greater burden on society than the crimes that prompt it, then you likewise want to keep people locked up for the minimum reasonable amount of time, because there are substantial ongoing costs for keeping them imprisoned - both financial, and societal.

Unfortunately, in this country currently the prison system is not truly operated as a public good and service, but rather it functions chiefly as a for-profit business.

Unknown said...

Actually, my point was more about whether and how we should listen to studies like this. If we were really going to be guided by this study, wouldn't we be keeping the current prison population locked up indefinitely? And if we don't, but use it to justify sentencing reform, aren't we really just using the study to rationalize what we want to do anyway? Again, I'm not actually suggesting we keep the current prison population locked up indefinitely--I'm critiquing the way we use studies.

John said...

The compares the status quo with proposed reforms that would reduce the prison population. It does not consider any other alternative, because no other alternative is really under consideration. It does not consider, for example, that we simply shoot all prisoners, even if that might reduce crime.

The study is narrowly focused on a single question: if we introduce reforms that would reduce the prison population 5 to 20 percent compared to current practice, would crime increase? The answer it finds is no. It is not intended to answer any other question.

Unknown said...

Indeed, but the author's analysis cites other studies that run into the problem I'm describing. Again, I'm not actually trying to say one thing or the other about prison reform. I am saying I think the value of statistical studies is limited.