With another contentious debate about immigration approaching for the new Congress, it's worth remembering that immigration doesn't benefit everyone equally. Immigrants are better off when they can come here freely, of course, and so are most people already in the country, who benefit from immigrants' skills and labor.

Theoretically, though, immigration could make life harder for workers with less skill and education if immigration reform forced those born in the United States to compete  for jobs with other less-skilled workers from around the world.

For these reasons, David Frum worries that advocates of immigration reform are relying on wishful thinking, ignoring "the real world" and "actual observed data" about the plight of less-skilled, native-born workers.

In fact, there is abundant evidence from the real world about whether immigration changes wages for relatively uneducated native workers, or pushes them out of work. Yet while some research does find that immigration leaves native blue-collar workers worse off, the effects seem to be small.

"Most research does not find quantitatively important effects on native wage levels or the wage distribution," economists Francine D. Blau and Lawrence M. Kahn have written.

Take Israel, which was overwhelmed with immigrants after the Soviet Union collapsed. One study found that despite the huge influx, which increased Israel's population by a whopping 1.4 percent a year for several years after 1989, the wages of workers already in Israel did not decline. Another found a decline in wages for blue-collar workers of between 1 percent and 3 percent for four to seven years.

American researchers haven't found different results. In U.S. cities with large numbers of immigrants, like Los Angeles and Miami, one study also found that immigration decreased wages for native workers by between 1 percent and 3 percent. According to a paper by Giovanni Peri of the University of California, Davis, immigrants had in fact raised wages for less skilled native workers, although only by a sliver (0.04 percent).

"The consensus is close to zero," Peri said.

One explanation could be that if firms are paying their immigrant workers less, they can use the savings to create new positions for their native employees. This groups is assigned supervisory or managerial work that takes advantage of their unique skills (such as speaking English) and allows the firm to operate more efficiently while employing more people.

Whether or not immigration raises or lowers wages for native, less skilled workers, Peri noted that unskilled workers stopped migrating into the United States after 2007, when the financial crisis made work here more difficult to find.

Since then, most immigrants have been highly skilled. Their presence in the country isn't likely to have much effect on blue-collar workers in any case, so it's hard to see how, as Frum suggests, immigration could be the reason that fewer American men have been working in the past few years.