"If only flows related to drug trafficking and other transnational organized crime activities were considered, related proceeds would have been equivalent to around US$650 billion per year in the first decade of the new millennium, equivalent to 1.5% of global GDP or US$870 billion in 2009 assuming that the proportions remained unchanged. The funds available for laundering through the financial system would have been equivalent to some 1% of global GDP or US$580 billion in 2009.
"The largest income for transnational organized crime comes from illicit drugs, which account for some 20% (17%-25%) of all crime proceeds, about half of transnational organized crime proceeds and 0.6% to 0.9% of global GDP. In turn, drug-related proceeds available for money-laundering through the financial system would be equivalent to between 0.4% and 0.6% of global GDP."
UN Office on Drugs and Crime, "Estimating Illicit Financial Flows Resulting from Drug Trafficking and Other Transnational Organized Crimes," Oct. 2011, p. 7.