According to a recent article in “The Economist”:
With less than 5% of the world’s population, the United States holds roughly a quarter of its prisoners: more than 2.3m people, including 1.6m in state and federal prisons and over 700,000 in local jails and immigration pens. Per head, the incarceration rate in the land of the free has risen seven-fold since the 1970s, and is now five times Britain’s, nine times Germany’s and 14 times Japan’s. At any one time, one American adult in 35 is in prison, on parole or on probation. A third of African-American men can expect to be locked up at some point, and one in nine black children has a parent behind bars.”
Furthermore, the article notes that mass incarceration has contributed to the breakdown of working-class families, especially black ones:
Among African-Americans aged 25-54, there are only 83 free men for every 100 women, which is one reason why so many black mothers raise children alone. Men behind bars cannot support their offspring, and when they are released, many states make it preposterously hard for them to find jobs. No surprise that the highest rates of incarceration are in the Deep South.