not only did they have you killing each other, they had you singing and dancing about killing each other...,

theatlantic |  The dramatic rise of incarceration and the precipitous fall in crime have shaped the landscape of American criminal justice over the last two decades. Both have been unprecedented. Many believe that the explosion in incarceration created the crime drop. In fact, the enormous growth in imprisonment only had a limited impact. And, for the past thirteen years, it has passed the point of diminishing returns, making no effective difference. We now know that we can reduce our prison populations and simultaneously reduce crime.

This has profound implications for criminal justice policy: We lock up millions of people in an effort to fight crime. But this is not working.

The link between rising incarceration and falling crime seems logical. Draconian penalties and a startling expansion in prison capacity were advertised as measures that would bring down crime. That’s what happened, right?

Not so fast. There is wide agreement that we do not yet fully know what caused crime to drop. Theories abound, from an aging population to growing police forces to reducing lead in the air. A jumble of data and theories makes it hard to sort out this big, if happy, mystery. And it has been especially difficult to pin down the role of growing incarceration.

So incarceration skyrocketed and crime was in free fall. But conflating simple correlation with causation in this case is a costly mistake. A report from the Brennan Center for Justice at NYU School of Law, called What Caused the Crime Decline? finds that increasing incarceration is not the answer. As Nobel laureate economist Joseph Stiglitz writes in the foreword, “This prodigious rate of incarceration is not only inhumane, it is economic folly.”

Our team of economic and criminal justice researchers spent the last 20 months testing fourteen popular theories for the crime decline. We delved deep into over 30 years of data collected from all 50 states and the 50 largest cities. The results are sharply etched: We do not know with precision what caused the crime decline, but the growth in incarceration played only a minor role, and now has a negligible impact.