"Globally, it is estimated that in 2012, between 162 million and 324 million people, corresponding to between 3.5 per cent and 7.0 per cent of the world population aged 15-64, had used an illicit drug — mainly a substance belonging to the cannabis, opioid, cocaine or amphetamine-type stimulants group — at least once in the previous year.

The extent of problem drug use - by regular drug users and those with drug use disorders or dependence remains stable at between 16 million and 39 million people."

http://www.unodc.org/documents/wdr2014/World_Drug_Report_201...