The US prison population has quadrupled since the 1980s, and almost half of those in federal prison are there for drug related crimes.
Over the last two decades, the U.S. prison population has quadrupled, with some 1.9 million people behind bars in federal and state prisons, and local jails by the year 2000.
Over the last 25 years, the prison population has quadrupled.
The country which has taken this furthest is the United States, where the prison population has quadrupled over the past three decades to 1.6m, and where crime rates have recently been falling in many big cities.
The study, by Human Rights Watch, concludes that jails and prisons have become the nation's default mental health system, as more state hospitals have closed and as the country's prison system has quadrupled over the past 30 years.
In particular, Obama called for shorter minimum mandatory sentences for nonviolent drug offenses, citing the sentences as the reason that the prison population has quadrupled from 500,000 in 1980 to more than 2.2 million today.
The prison population has quadrupled since 1980.
Since 1980, the U.S. prison population has quadrupled to well over 2 million, an increase largely driven by heavier penalties for non-violent offenses.
Since then the federal prison population has quadrupled; more than half of all federal inmates were sentenced using mandatory minimum laws.
Owing largely to overcriminalization, the nation's prison population has quadrupled since 1980 to 2.4 million, which breaks down to more than one out of every 100 American adults behind bars.
