Around 24 years ago, crime rates in the US started to mysteriously decline. Since then, crime has fallen by roughly half, with violent crimes plummeting by roughly 51 percent and property crimes decreasing by about 43 percent.
Almost as soon as the crime decline began, criminologists started trying to figure out the reasons. Different theories have come in and out of vogue over the past couple of decades. Some theories, such as mass incarceration, seemed very sound in the 1990s, but have been called into question as more data has come in. Some surprising theories, such as one related to the decreasing lead content in gasoline, have recently gained momentum.
In a massive report released in February 2015, the Brennan Center for Justice looked at more than a dozen of these explanations and ran statistical analyses to show how much of the crime decline can be attributed to each one of them. Their conclusion is that a lot of things had some effect on crime in the 1990s — but there was no smoking gun.
But even the Brennan report, by its own admission, only tells part of the story. It didn’t account for some additional theories touted by criminal justice experts, such as the idea that technology keeps people indoors. So we rounded up some of the Brennan Center’s ideas, plus a few they didn’t mention, to analyze 16 popular theories for the plummeting crime rate.
1) More criminals are getting put in prison
The case for: It seems intuitive. The incarceration rate’s been rising; the crime rate’s been falling. Surely this is because people are being locked up who’d otherwise be committing crimes out on the streets.
Several academic studies have found that increased incarceration had a big impact on reducing crime. In particular, Steven Levitt (of Freakonomics fame) wrote a paper in 2004 that concluded that 58 percent of the drop in violent crime during the 1990s was due to incarceration.
The case against: These studies were based on older data that only included a few years of the crime decline. Levitt acknowledged he couldn’t account for the point of diminishing returns: there are only so many serious criminals out there, and after a certain point the people getting put in prison aren’t people who’d be committing crime after crime on the street. The higher the incarceration rate gets, the less it matters if you increase that rate even more. Studies that examine more recent data, after the point of diminishing returns has been hit, find that incarceration wasn’t nearly as influential.
“Incarcerating violent people has a big effect on violence,” John Roman, senior fellow at the Urban Institute’s Justice Policy Center, said. “But most people we incarcerate aren’t violent.”
The diminishing returns aren’t only about who’s being put in prison, but how long people remain there. The research suggests that people age out of crime, so letting them out of prison 10 or 20 years down the line — instead of the longer sentences applied today — might not pose a threat to public safety. “Crime is a young man’s endeavor,” Brian Elderbroom, senior fellow at the Urban Institute’s Justice Policy Center, said in December. “It’s not surprising that someone who commits a crime at a young age would be a completely different person by the time they’re in their 30s.”
The other problem with this theory is that incarceration rates were increasing for years before crime started going down.
The bottom line: A small effect. Criminologists now tend to believe that incarceration accounts for a fraction of the drop in crime, but no more. The Brennan Center report estimates that incarceration played even less of a role than that: up to 12 percent of the drop in property crime during the 1990s was due to the rise in incarceration, but it was probably more like 6 percent. And it contributed to 1 percent, at most, of the continued property crime decline in the 2000s. Furthermore, the Brennan Center concluded that the rising incarceration rates through the 1980s had already locked up the truly violent criminals, and the point of diminishing returns was hit even before the crime rate started to fall.
Source: Vox.com | Dara Lind