Ezra Klein, writing in...

...Bloomberg today, provides a nice, short history of immigration from Mexico. And some of it may surprise you. For starters, according to Douglas Massey (above), a professor at Princeton, everything you think you know about immigration is probably wrong. For example (my emphasis):

According to Massey, the rise of America’s large undocumented population is a direct result of the militarization of the border. While undocumented workers once traveled back and forth from Mexico with relative ease, after the border was garrisoned, immigrants from Mexico crossed the border and stayed.

“Migrants quite rationally responded to the increased costs and risks by minimizing the number of times they crossed the border,” Massey wrote in his 2007 paper “Understanding America’s Immigration ‘Crisis.’” “But they achieved this goal not by remaining in Mexico and abandoning their intention to migrate to the U.S., but by hunkering down and staying once they had run the gauntlet at the border and made it to their final destination.”

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.