Jailhouse nation

How to make America’s penal system less punitive and more effective. 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...