The U.S. incarceration rate has more than quadrupled since 1980. It's now the highest in the world, just ahead of Russia and Rwanda. It is estimated that approximately 2.3 million Americans are now behind bars. This is about one-fourth of all the incarcerated people on Earth, though the U.S. represents only one-twentieth of the world's population. When the figures for those under probation and parole are added, about 1 in 18 U.S. men is under some form of monitoring or control. The figure for blacks is 1 in 11.
From a medical point of view, the number 2.3 million is huge. It is double the number of Americans infected with HIV, the virus that causes AIDS. People in prison are much more likely to carry and contract a variety of communicable diseases, including tuberculosis, syphilis, and hepatitis B and C. Recent articles in The Atlantic have detailed horrible prison conditions and egregious abuses of mentally ill prisoners. From a medical perspective, putting someone in prison is putting them in harm's way.
Why have U.S. incarceration rates skyrocketed? The answer is not rising crime rates. In fact, crime rates have actually dropped by more than a quarter over the past 40 years. Some look at these statistics and find confirmation of their view that expanding prison populations reduces crime rates. In fact, however, these same decreases have occurred even in places where incarceration rates have remained unchanged.