Trump is obsessed with an immigration crisis that's already over

As the Pew Research Center has illustrated with data, illegal immigrants are also leaving the U.S. since 2007 faster than have been coming in. And there are fewer illegal Mexican immigrants in the United States today than there were in 2005.

Why? A major reason is that Mexico, the largest source of illegal immigrants to the U.S., became a better place to live. It shed its socialistic one-party political system in the late 1990s and adopted the very sort of free-trade policies that Trump now criticizes. Mexico signed free trade agreements with 44 different countries. Its exports increased six-fold. The share of Mexicans surviving on less than two dollars per day plunged from 20 percent in 1996 to just 4 percent in 2012.

Thus, the economic desperation that causes mass migration from Mexico has declined. Meanwhile, Mexico’s new crackdown on Central American immigrant traffic will likely lower the rate of illegal immigration to the U.S. even further.