"Cannabis remains by far the most commonly used drug in the world."
An estimated 162 million people used cannabis in 2004, equivalent to some 4 per cent of the global population age 15-64. In relative terms, cannabis use is most prevalent in Oceania, followed by North America and Africa.
While Asia has the lowest prevalence expressed as part of the population, in absolute terms it is the region that is home to some 52 million cannabis users, more than a third of the estimated total.
The next largest markets, in absolute terms, are Africa and North America." Source: United Nations Office on Drugs and Crime, "World Drug Report 2006, Volume 1: Analysis" (United Nations: Vienna, Austria, 2006), p. 23