http://www.stratfor.com/graphic_of_t...10-arms-mexico
(original includes pie-chart with the numbers)
Snippet:

Debunking Mexico's Arms Myth
February 10, 2011 | 1800 GMT
There is a long and well-documented history of arms smuggling across the U.S.-Mexico border, and while the United States is a significant source of certain classes of weapons and ammunition, it is by no means the source of 90 percent of the weapons used by the Mexican cartels, as is commonly asserted.