Illegal drugs are substances sold and purchased on the black market. The United Nations has estimated that the illegal drug trade accounts for about 1% of all global trade. Heroin, cocaine, methamphetamine, and marijuana are the major illegal drugs bought and sold around the world.
The first bans against opium smoking took place in China in 1729. Most western nations did not have prohibitions against drugs until the 19th century. Opium was restricted in the UK with the 1868 Pharmacy Act, and in the United States in 1914 with the Harrison Act. Marijuana was classified as a Schedule I narcotic in the 1930s.
Demand for illegal drugs such as marijuana and cocaine has risen sharply in the first years of the 21st century. As a result, complex networks of smuggling exist across the globe. Cocaine is produced in Colombia and Bolivia, for example, and smuggled through West Africa and into Europe. Cocaine is also smuggled into North America through Central America. This has led to the rise of violent cartels in Central America, especially in Mexico, which experiences unprecedented levels of narcoterrorism along the US border.
Heroin, on the other hand, is largely produced in Afghanistan, with that nation replacing the Golden Triangle as the world's leading poppy producer. Much of the world's heroin is then smuggled through Iran into Europe and then the United States.