In the U.S. immigration debate, we have thus far focused our attention on the symptom—Mexicans crossing the semi-permeable barrier into the United States—and treated the crossing itself as the problem to be solved. In other words, policy makers have been preoccupied with figuring out how to make the border less permeable. But this is a fool’s errand. It’s time to start looking at the pressures that drive unidirectional movement instead of at the symptom.