The World Drug Report presents a comprehensive annual overview of the latest developments in the world’s illicit drug markets by focusing on the production, trafficking and consumption of the main types of illicit drugs, along with the related health consequences of those drugs. Despite the fact that increasing professionalism and sophistication have enhanced the capacity of cannabis plant growers to avoid detection by law enforcement authorities, data for 2013 show an increase in the quantities of cannabis herb and cannabis resin seized worldwide.

http://www.unodc.org/documents/wdr2015/World_Drug_Report_2015.pdf