Making marijuana available north of the border could cut off revenue for drug trafficking organizations to the south of it.

Mexico and the U.S. are tightly entwined economically -- and this is as true of the illegal economy as the legal one. If popular ballot measures to legalize marijuana in Colorado, Washington and Oregon pass on November 6, a respected Mexican think tank says that it will hit the cartels where it hurts: In the pocketbook, to the tune of several billion dollars. While tough police and military operations on both sides of the border have largely failed to slow the cartels, legalization would be "the biggest structural shock suffered by drug trafficking in Mexico since the massive arrival of cocaine in the late eighties," the researchers wrote.

The report from the Mexican Center for Competitiveness (IMCO) (in Spanish) is based on an earlier study by the RAND Corporation, which determined that a 2010 ballot proposal could cut the income of Mexican drug dealers by 20%. The updated research suggests that cartels earn $6 billion each year from marijuana sales in the United States. If Washington, the state most likely to pass its ballot measure, does so, IMCO reports it will cut the cartels' income by $1.37 billion, or about 23% of their revenue (though some cartels will be hit harder than others). Legalization in Oregon and Colorado would result in similar declines.