From the drug trade, Mexican gangs gained ______ from the US each year.

Mexican drug gangs have expanded their activities in the US with heroin production doubling this year, the US justice department says in a report. Despite US funding for the war on drugs, trade in marijuana and ecstasy also grew, the National Drug Threat Assessment said. The report found that Mexican groups were active in every region of the US. Gangs were moving an estimated $40bn in cash back into Mexico across the border each year, it added. Mexico has long been the main channel for illicit drugs smuggled into the US but this report suggests that the efforts to halt the flow on both sides of the border have had only a limited impact. In 2007 the US pledged $1.4bn over three years to fight the drug gangs but the following year heroin production in Mexico rose from 17 to 38 metric tonnes. This, the report says, led to lower heroin prices and more overdose deaths in the US.