The incarceration rate in the United States has undergone an unprecedented surge since the 1970s. Between 1925 and 1975, the U.S. incarceration rate hovered around 100 per 100,000. Since then, that rate soared to 504 in 2009, dropping only slightly to 500 in 2010. In absolute numbers, the U.S. prison population grew from 241,000 in 1975 to 1.55 million in 2010. Not just exceptional by historical standards, this boom is unparalleled globally: the United States has the highest incarceration rate in the world. Despite having just 5 percent of the world’s population, it houses nearly 25 percent of the world’s prisoners.
It is not surprising that academics, journalists, and policymakers have attempted to explain the causes of this growth. What is surprising, however, is the general weakness of such explanations. The formal empirical papers that tackle the issue, for example, all suffer from severe methodological shortcomings that fundamentally undermine their results. Many of the common explanations—that prison growth is due to the war on drugs, to parole and probation violations, to longer sentences—are often asserted with little rigorous empirical support. And as I have pointed out before, and will continue to do so here, this conventional wisdom is frequently wrong. A recent entry in this discussion is Ernest Drucker’s A Plague of Prisons: The Epidemiology of Mass Incarceration in America. An epidemiologist by training, Drucker attempts to use epidemiology’s tools to shed new light on the complex causal roots of today’s mass incarceration problem. While he largely fails in his efforts, he does so in a very useful way: the mistakes he makes are ones that permeate this literature, so that identifying and correcting them serves the broader goal of setting the record straight(er) about the causes and effects of prison growth.