"One flaw of current U.S.-Mexico strategy is the false presumption that international trafficking of drugs, guns, and cash can be effectively addressed through interdiction, particularly along the nearly two thousand- mile U.S.-Mexico border. After a three-decade effort to beef up security, the border is more heavily fortified than at any point since the U.S.-Mexico war of 1846–48. The United States has deployed more than twenty thousand border patrol agents and built hundreds of miles of fencing equipped with high-tech surveillance equipment, all at an annual cost of tens of billions of dollars. Although this massive security buildup at the border has yielded the highest possible operational control, the damage to Mexico’s drug cartels caused by border interdiction has been inconsequential.43 Meanwhile, heightened interdiction at the border has had several unintended consequences, including added hassles and delays that obstruct billions of dollars in legitimate commerce each year, the expansion and increased sophistication of cross-border smuggling operations, and greater U.S. vulnerability to attacks and even infiltration by traffickers.44 Further efforts to beef up the border through more patrolling and fencing will have diminishing returns, and will likely cause more economic harm than gains in security for the struggling communities of the border region.45"

Source

Shirk, David A., "Drug War in Mexico: Confronting a Shared Threat," Council on Foreign Relations, Center for Preventive Action (Washington, DC: March 2011), p. 18.
http://i.cfr.org/content/publ…