Speaking Thursday before the U.S. Sentencing Commission, Holder said he supported the commission's proposal, which could reduce the federal prison population by 6,500 inmates in the next five years.
The change, Holder said, would "make the federal criminal justice system both more effective and more efficient when battling crime and the conditions and behaviors that breed it."
The move is part of a broader effort to ease burdens on an overcrowded prison system and reduce costs, as well as making the justice system more fair. Another recent effort has moved to reduce mandatory minimum sentences for certain non-violent drug offenses, which have tended to weigh more heavily on minorities.
"This overreliance on incarceration is not just financially unsustainable -- it comes with human and moral costs that are impossible to calculate," Holder said.
With just 5 percent of the world's population, the U.S. has almost 25 percent of the world's prisoners.
[Department of Justice]