A 2007 paper by Douglas Massey argued that undocumented immigrants have responded to increased border security “by hunkering down and staying once they had run the gauntlet at the border and made it to their final destination.” Ezra finds that the “data support Massey’s thesis”:
In 1980, 46 percent of undocumented Mexican migrants returned to Mexico within 12 months. By 2007, that was down to 7 percent. As a result, the permanent undocumented population exploded.
The militarization also had another unintended consequence: It dispersed the undocumented population. Prior to 1986, about 85 percent of Mexicans who entered the U.S. settled in California, Texas or Illinois, and more than two-thirds entered through either the San Diego-Tijuana entry point or the El Paso-Juarez entry point. As the U.S. blockaded those areas, undocumented migrants found new ways in — and new places to settle. By 2002, two-thirds of undocumented migrants were entering at a non-San Diego/El Paso entry point and settling in a “nontraditional” state.
Steven Taylor adds:
I will say that I think that dispersal of migrants is also attributable to increasing demands for labor in agriculture across the country (such as working in poultry in Alabama or in labor-intensive crop-picking jobs across the southeast). However, the hypothesis makes sense: if one cannot return home without risking trouble with la migra, then it is best to look stay put (not to mention to get away from places where border enforcement is being intensely focused).