Explain the socioeconomic roots of the international drug trade

The order of magnitude of the extent of the illicit drug problem should be established in the light of at least two of the unique characteristics of illicit drugs: first social wise, they are all addictive substances, a fact that sometimes blurs the dividing line both between use and abuse and between consumption and addiction; and secondly economically, though commodities that are traded or trafficked, they are distinguished by low volume but enormously high unit cost and value. 

The answer should be europe