Barack Obama has laid out sweeping reform proposals on the US criminal justice system this week in the hope of reducing the country's prison population.

As part of a week-long focus on the issue, Obama will become the first serving US president to visit a federal prison when he travels to El Reno Correctional Institution in Oklahoma.

In a speech to the National Association for Advancement of Coloured People (NAACP) on Monday, Obama called on voting rights to be restored to those in prison and to reduce the use of solitary confinement.

The president believes that too many young black and Latino men are over-represented in the US prison population and are being treated differently to their white peers.

In addition, as this chart from Statista shows, 25 per cent of the world’s prisoners are based in US jails and the country has a higher ratio of prisoners than any other country in the world (apart from the small island nation of the Seychelles).