The Pew Research Center reports that the illegal immigrant population is back on the rise, from 11.5 million in 2011 to 11.7 million in 2012. These are estimates, and the Pew people provide appropriate caveats and range. The illegal population peaked at 12.2 in 2007, then fell to 11.3 million in 2009 and now is apparently on the rise.

Mickey Kaus takes a poke at me for my prediction (admittedly subject to refutation) that we will never see anything like the huge wave of immigration, legal and illegal, from Mexico that we saw in the quarter-century from 1982 to 2007. This prediction was prompted by research for my book, out Oct. 1, "Shaping Our Nation: How Surges of Migration Transformed America and Its Politics." I found that previous surges of immigration and internal migration sometimes ended abruptly and that almost no one predicted their abrupt ends. The huge Irish and German immigration that started in the 1840s petered out in the economically troubled early 1890s and never resumed at previous levels. The huge migration of American blacks from the rural South to the urban North, which started in 1940, ended abruptly in 1965, when everyone assumed it would just go on and on. There was a huge migration of Puerto Ricans to New York starting about 1949 that ended abruptly in 1961, and of course Puerto Ricans as American citizens could come any time.

I don’t think the Pew report contradicts my prediction about Mexicans. Their estimate of the illegal Mexican population is continuing to decline, from 6.9 million in 2007 to 6.2 million in 2011 and 6.0 million in 2012. The illegal population from other countries, they estimate, peaked at 5.3 million in 2007, fell to 5.0 million in 2009, then rose back to 5.3 million in 2011 and increased again to 5.7 million in 2012.

Mickey Kaus notes this, writing, “Note that even if the mild U.S. economic recovery is the sole cause of the increase, that would seem to confirm that a job market most Americans regard as pretty crappy can still be highly appealing to millions of potential illegal entrants from poorer nations, some (e.g. those in Central America) within walking distance.” That’s a fair point. But there’s a lot of walking distance between Central America and the U.S.-Mexico border. Mexican laws are tough on illegal immigrants and Mexican law enforcement is not rigorously disciplined by a Mexican Civil Liberties Union. And the reservoir of potential immigrants from Central America is smaller than that from Mexico (total population: Central America, 44 million, Mexico, 118 million).

Better U.S. border enforcement could make a difference here. But what is really needed to discourage illegal immigration is workplace enforcement through some difficult-to-forge identification card and other high-tech devices. Mexican immigrants, legal and illegal, have been more downscale in education and skill levels than those from any other country, presumably because they start off in relative proximity to our land border. If you’re worried about downscale illegal (and legal) immigration, as Mickey is, the trends Pew shows should be mildly encouraging.