Tough sentencing laws, record numbers of drug offenders and high crime rates have contributed to the United States having the largest prison population and the highest rate of incarceration in the world, according to criminal justice experts.
A US Justice Department report released on November 30th showed that a record 7 million people - or one in every 32 American adults - were behind bars, on probation or on parole at the end of last year.
Of the total, 2.2 million were in prison or jail. According to the International Centre for Prison Studies at King's College in London, more people are behind bars in the United States than in any other country. China ranks second with 1.5 million prisoners, followed by Russia with 870,000.
The US incarceration rate of 737 per 100,000 people in the highest, followed by 611 in Russia and 547 for St Kitts and Nevis.
In contrast, the incarceration rates in many Western industrial nations range around 100 per 100,000 people. Groups advocating reform of US sentencing laws seized on the latest US prison population figures showing admissions of inmates have been rising even faster than the numbers of prisoners who have been released.
"The United States has 5 percent of the world's population and 25 per cent of the world's incarcerated population. We rank first in the world in locking up our fellow citizens," said Ethan Nadelmann of the Drug Policy Alliance, which supports alternatives in the war on drugs.
"We now imprison more people for drug law violations than all of western Europe, with a much larger population, incarcerates for all offenses." Ryan King, a policy analyst at The Sentencing Project, a group advocating sentencing reform, said the United States has a more punitive criminal justice system than other countries.