Over at FiveThirtyEight, Ben Casselman has a good article on something I've also written about: the changing patterns of immigration. The debate on comprehensive immigration legislation, as he notes and I have noted, has remained much the same since bills came before the Senate in 2006 and 2007. But the facts have changed. Net migration from Mexico to the United States fell to zero between 2007 and 2012 (the latest year covered by data), according to the Pew Research Center. There are now more immigrants coming from Asia than from Latin America, contrary to the 1982-2007 period. There has been a decline, about 10 percent in magnitude, in the number of illegal immigrants living in the United States.

And of course in recent months we have seen a huge spike in underage illegal immigrants from Guatemala, Honduras and El Salvador.

What do these changes mean for policy? I think they mean that border enforcement is not as important as most Republicans and some Democrats think. This is subject to the caveat that the flood of underage Central Americans needs to be addressed, presumably by expanding the list of countries to which illegal underage immigrants can be returned to include Guatemala, Honduras and El Salvador — something Barack Obama seemed inclined to favor but now, after meeting with Latino activist group leaders, appears to oppose.

Overall, an increasing percentage of immigrants seem to be high-skilled immigrants — a trend that we should encourage and strengthen, I have argued, by adopting a system similar to those in Canada and Australia which give priority to high-skill immigrants. Market forces are already moving in this direction, apparently — a recognition of the fact that there aren't lots of low-skill jobs looking for applicants these days — and we should use that fact to move the system in that direction. And not just by increasing the number of H-1B visas, which must be sought by employers, but by letting in more high-skill people and letting them make their way in our free market economy.

As I note in my recent book, Shaping Our Nation: How Surges of Migration Transformed America and Its Politics, migration patterns have often shifted sharply, and in ways no one predicted, in the course of American history. Intelligent policymakers should be alert to such changes and respond in ways that strengthen the nation.