In Episode 5 of the third season of Revisionist History, Malcom Gladwell makes the case that tightening the border control between the United States and Mexico led to more instead of less immigration to the US. I find that a fascinating and compelling argument. With open borders and low costs associated to crossing, there is lots of seasonal going in and out, but very little net migration. Workers who can earn a good wage in the US mostly still want to return back to their families whenever they can. Crossing the border was easy in the 70s and 80s, but US authorities tightened the screws over time. With the cost of entering the US gradually increasing, circular and thereby temporary migrants hesitated to return to Mexico, not sure if they could ever go back and work in the States again. Instead of traveling back and forth, Mexican’s already accustomed to working in the US oftentimes simply settled down permanently, thereby increasing the net influx of immigrants. The claim is supported by research based on the Mexican Migration Project (The page is quite an interesting artifact of the 90s world wide web. But if you want to dig deeper, they have a long list of publications).