About 7 million adults — accounting for 3% of the U.S. population — were incarcerated, on probation or on parole at the end of 2005, the Justice Department said Thursday.

Of that total, 2.2 million individuals were in federal and state prisons or local jails, 4.1 million were on probation and more than 784,000 were on parole.

Drug crimes — up 64.8% from 1996 to 2003 — accounted for the largest increase in the number of inmates in the federal system.