"Since sentenced prisoners made up 96% of the prison population in 2011, it was expected that the changes in the sentenced prison population in 2011 mirrored those in the total prison population. The total number of sentenced prisoners declined by 1.0%, and the sentenced prison population in the federal system increased by 3.4%. The sentenced state prison population declined by 1.6%.
"Between 2010 and 2011, the imprisonment rate—the number of sentenced prisoners divided by the U.S. resident population times 100,000—declined from 500 to 492 per 100,000 U.S. residents (table 6). The imprisonment rate has declined consistently since 2007 when there were 506 persons imprisoned per 100,000 U.S. residents. The rate in 2011 was comparable to the rate observed in 2005 (492 per 100,000)."
Carson, E. Ann, and Sabol, William J., "Prisoners in 2011" (Washington, DC: US Dept. of Justice Bureau of Justice Statistics, Dec. 2012), NCJ239808, p. 6.