Does Incarceration Stop Crime in America?

Source: Thinkstock

Source: Thinkstock

The United States has 2.3 million people incarcerated. With one in 100 American adults locked up, we have the world’s highest incarceration rate, one that’s nine to 10 times that of many European countries. In the most general terms, we aren’t hesitant to send people to prison. Some may think our high incarceration rate has contributed to the decline in crime we’ve seen in the past 20 years or so, but that might not be the case at all. A recent study that reviewed data from every state and the 50 largest cities in the U.S. found that incarceration has not been the reason for a decline in crime over the past few decades.

The report, “What Caused the Crime Decline?”, concluded that “over-harsh criminal justice policies, particularly increased incarceration, which rose even more dramatically over the same period, were not the main drivers of the crime decline,” according to the Brennan Center for Justice. Rather, the report finds other reasons for the decline are social, economic, and environmental factors, like higher incomes and an aging population. But let’s take a closer look at what could be slowing down crime, and what the actual effects of mass incarceration are.

Why incarceration isn’t stopping crime

2004 paper from Steven Levitt, author of Freakonomics, attributed 58% of the drop in violent crime during the 1990s to incarceration. The Brennan Center’s report takes quite a different stance — it estimates that incarceration caused only up to 12% of the drop in property crime during the 1990s and at most 1% of the continued property crime decline in the 2000s.

The Brennan Center concedes that the increase in incarceration in the 1980s locked up many violent criminals, contributing to a decrease in violent crime then, but doesn’t think that correlation continued into the ’90s to the extent that Levitt suggests. Rather, the Brennan Center report suggests that 0% to 7% of the crime decline in the 1990s and less than 1% in the 2000s.

What has slowed crime?

The report from the Brennan Center suggests other possible factors that affect crime rates, but they all seem to have a small effect (or it’s unclear whether they have an effect at all, but theoretically they could). One suggestion throughout the report is that the population is aging out of crime. It only suggests a small effect, but the report finds that between 2 to 3% of the crime drop in the 1990s can be attributed to a decrease in people aged 15 to 29, the age range most likely to commit crimes. This probably didn’t continue to affect crime decline in the 2000s, as there wasn’t a significant change in the proportion of this age group from 2000 to 2010.

Another factor the Brennan Center thinks may have a small effect is the amount of police on the streets. The report found that increases in the number of police officers may have been responsible for 0 to 10% of the crime decline in the 1990s, but this effect probably didn’t continue in the 2000s as police numbers did not continue to increase. Vox points out the circular nature of this factor though: “… while the number of police can affect crime rates, crime rates also affect the number of police. When crime rises, cities hire more police in response. It’s extremely tricky to isolate the effect of police on crime from the effect of crime on police.”

Growth in income is a factor the Brennan Center sees as having slightly more of an effect. The report shows that it was responsible for 5 to 10% of the drop in crime in both the ’90s and the 2000s. However, Vox notes that general improvements in the economy have an unclear effect on crime, as crime continued to decline despite the recession and rise in unemployment beginning in 2008.

Is mass incarceration bad for society?

Prison is expensive. It’s been said again and again. In 2012, the Vera Institute of Justice estimated that the total price of the prison system to taxpayers was $39 billion. A 2013 study showed that it cost New York City nearly $170,000 per inmate. And the costs of incarceration in the U.S. are often compared to those of education. In every single state, it is vastly more expensive to incarcerate a person than to send them to college. (This statistic comes up again and again as public funding for higher education evaporates.)

The report suggests that, considering the costs of mass incarceration, both fiscal and social, it may be better to create programs that improve economic opportunities, modernize policing practices, and expand treatment and rehabilitation programs. These could be a better public safety investment, the Brennan Center says.

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