Between 1996 and 2006, as the U.S. population rose by 12 percent, the number of adults incarcerated rose by 33 percent to 2.3 million inmates, and the number of inmates who were substance involved shot up by 43 percent to 1.9 million inmates.

Of the 2.3 million inmates in U.S. prisons, 65% — 1.5 million meet the DSM-IV medical criteria for alcohol or other drug abuse and addiction. Another 20 percent — 458,000 — even though they don’t meet the DSM-IV medical criteria for alcohol and other drug abuse and addiction nevertheless were substance involved; i.e. were under the influence of alcohol or other drugs at the time of their offense, stole money to buy drugs, are substance abusers, violated the alcohol or drug laws, or share some combination of these characteristics.

Source: Behind Bars II: Substance Abuse and America’s Prison Population