In response to record numbers of illegal border crossings and the security fears triggered by the 9/11 attacks, over the past two decades the United States has steadily increased its efforts to secure its borders against illegal immigration. The number of U.S. Border Patrol agents has risen from fewer than 3,000 to more than 20,700; nearly 700 miles of fencing have been built along the southern border with Mexico; and surveillance systems, including pilotless drones, now monitor much of the rest of the border. In a speech in El Paso, Texas, in May, U.S. President Barack Obama claimed that the United States had "strengthened border security beyond what many believed was possible." Yet according to spring 2011 Rasmussen poll, nearly two-thirds of Americans think the border is no more, or even less, secure than it was five years ago. Some administration critics claim that the United States' frontiers have never been more porous.
This contradiction stems in part from the fact that the Department of Homeland Security (DHS) has never clearly defined what border control means in practice. A secure border cannot mean one with no illegal crossings -- that would be unrealistic for almost any country, especially one as big and as open as the United States. On the other hand, the borders cannot be considered secure if many of those attempting to enter illegally succeed. Defining a sensible middle ground, where border enforcement and other programs discourage many illegal crossings and most of those who try to cross illegally are apprehended, is the challenge.
Unfortunately, the U.S. government has failed to develop good measures for fixing goals and determining progress toward them. Since 2005, the DHS has reported how many miles of the country's land borders are under its "operational control," but it has done so without having clearly defined what that standard means and without providing hard data to back it up. The lack of sound measurement has left the administration touting its efforts rather than their results: during a press