The study produced five main findings. First, drug users in the United States spent approximately $100 billion annually on cocaine, heroin, marijuana, and meth. In 2000 significantly more money was spent on cocaine than marijuana; in 2010, the opposite was true. Second, from 2002 to 2010, the amount of marijuana consumed in the United States likely increased by approximately 40 percent, while the amount of cocaine consumed decreased by about 50 percent. Third, heroin consumption remained fairly stable throughout the decade, although there is some evidence of an increase in the later years. Most of the heroin consumed in the United States comes from poppies grown in Colombia and Mexico; however, data deficiencies on production from 2005 to 2010 make comparisons difficult. There was a steady increase in the amount of heroin seized within the United States, as well as at the southwest border from 2007 through 2010. Fourth, meth estimates are subject to the greatest uncertainty because national datasets do not perform well in documenting its use. Fifth, for all of the drugs included in the study, total consumption and expenditures were driven by the minority of heavy users, who consumed drugs on 21 or more days each month. For all four illicit drugs examined, the estimates drew on the complementary strengths of the National Survey on Drug Use and Health (NSDUH) and the Arrestee Drug Abuse Monitoring Program (ADAM), supplemented by a wide range of other data sources. 23 tables and 46 figures