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.

New sentencing guidelines have been a key factor. They have reduced judges' discretion in determining who goes to jail and increased the amount of time convicts sentenced to jail spend there. A notable example is the so-called "three-strikes" law, which mandates sentences ranging from 25 years to life for many repeat offenders. Though championed as protecting the public, such sentences have resulted in long confinements for many non-violent offenders, who constitute half of all inmates.

Perhaps the single greatest contributor has been the so-called "war on drugs," which has precipitated a 12-fold increase in the number of incarcerated drug offenders. About 1.5 million Americans are arrested each year for drug offenses, one-third of whom end up in prison. Many are repeat offenders caught with small quantities of relatively innocuous drugs, such as marijuana, a type of criminal activity often referred to as "victimless."

Some sentencing laws seem little less than perverse. For example, in the 1980s, crack cocaine received a great deal of public attention. In response, the U.S. Congress passed legislation imposing a 100 to 1 sentencing ratio for possession of crack cocaine, as compared to its powdered form. That is, someone carrying 5 grams of crack cocaine would get the same sentence as someone carrying 500 grams of powdered cocaine. From a medical point of view, this makes little sense.