The United States contains 25% of the world's prison population, but only makes up about 5% of the total population (https://www.splcenter.org/issues/mass-incarceration). The inflated amount of prisoners has led to overcrowding of prisons, high government expenditures, and other related issues. However, many individuals and organizations have recognized this issue and have pushed for reforms in the criminal justice system. These reforms have translated into the 8.4% decrease in prison population in the United States from 2010-2015(http://thehill.com/homenews/news/312480-us-prison-population-falling-as-crime-rates-stay-low). So, there's progress. The United States still harbors a concerning proportion of the world's incarcerated population, though.
What types of reforms can and should be implemented in the United States and other countries to address the inflated prison populations?
What criminal justice reforms have effectively reduced the prison population in other countries?