Michael Barone notes that the most recent wave of migration might be petering out.  Looking back at past waves of immigration to America, he notes that experts always assume that the future will resemble the past, particularly the recent past, "almost no one predicted that these surges of migration would begin -- and almost no one predicted that they would stop when they did."

That might be true again:

From 1980 to 2008 more than 5 million Mexicans legally entered the United States. And Mexicans account for about 60 percent of the estimated 11 million illegal immigrants in the U.S. today.

Immigration policymakers have assumed that the flow of Mexican immigrants would continue indefinitely at this high level. But now evidence is accumulating that this vast surge of migration is ending.

The Pew Hispanic Center, analyzing census statistics, has estimated that illegal Mexican entrants have been reduced from 525,000 annually from 2000 to 2004 to 100,000 a year in 2010.

"The flow has already stopped," Douglas Massey of the Mexican Migration Project at Princeton University recently told the New York Times. "The net traffic has gone to zero and is probably a little bit negative."

Barone suspects that declining conditions in the U.S. and improved ones in Mexico account for the change.  If Barone is on target, it is an interesting and important trend.  He suggests it would allow us to focus our immigration policy on attracting more skilled and educated immigrants.  It might also give us time to assimilate the latest wave of immigrants.