The U.N. global arms talks come as a new study has revealed that about 2 percent of all U.S. gun sales are made to groups that smuggle them into Mexico. More than 250,000 U.S. guns head into Mexico each year as part of an illegal trade worth nearly $130 million annually, according to researchers at the University of San Diego. In fact, thousands of U.S. sellers depend on the illegal sales and would go out of business without them, the report found.