In 2000, police made 1,579,566 total arrests for drug abuse violations. 81%—or 1,279,448—of these total drug arrests were for possession. 46.5%—or 734,497 of all drug arrests—were for marijuana offenses. And of the total marijuana arrests, 646,042 (88%) were for possession alone.
Sources: Federal Bureau of Investigation, Uniform Crime Reports for the United States 2000 (Washington DC: US Government Printing Office, 2001), pp. 215-216, Tables 29 and 4.1.

The United States is the world leader in rate of incarceration. As of June 30, 2001 there were 1,965,495 inmates held in federal and state prisons and local jails, with an incarceration rate of 690 persons per 100,000. This places the U.S. ahead of second-place Russia (676 per 100,000) as the world leader in incarceration, both by rate and in absolute terms. Most nations in western Europe incarcerate their citizens at a rate ranging from 60-130 per 100,000.
Sources: The Sentencing Project analysis of the US Department of Justice, Bureau of Justice Statistics study, Prison and Jail Inmates at Midyear 2001.

Prisoners sentenced for drug offenses constitute the largest group of Federal inmates (61%) in 1999, up from 53% in 1990. On September 30, 1999, Federal prisons held 63,360 sentenced drug offenders, compared to 30,470 at yearend 1990.
Source: Beck, Allen J., PhD, US Department of Justice, Bureau of Justice Statistics, Prisoners in 1999 (Washington, DC: US Department of Justice, August 2000), p. 12 and Table 21.

Over 80% of the increase in the federal prison population from 1985 to 1995 was due to drug convictions.
Source:US Department of Justice, Bureau of Justice Statistics, Prisoners in 1996 (Washington DC: US Department of Justice, 1997).

In 1997, there were 55,069 drug offenders in federal prisons (out of a total Federal prison population of 88,018 that year). Of these, 10,094 were in for possession, 40,053 were in for trafficking, and 4,922 were in for other drug crimes.
Source:Mumola, Christopher J., "Substance Abuse and Treatment, State and Federal Prisoners, 1997" (Washington, DC: US Dept. of Justice, January 1999), p. 3, Table 1.

Nonviolent offenders accounted for eighty-four percent (84%) of the increase in state and federal prison admissions since 1980.
Source:Ambrosio, T. & Schiraldi, V., Executive Summary-February 1997 (Washington DC: The Justice Policy Institute, 1997).