By holding down natural wage growth in labor-intensive industries, immigration serves as a subsidy for low-wage, low-productivity ways of doing business, retarding technological progress and productivity growth.

The interesting point is that the polarization is not so much among the public, although there's some of that. The polarization on the immigration issue is really between the elites and the public. In other words, this is not so much a right-left issue, which it is partly.

In enforcement, you always have to have both a focus on the really worst actors - you know, gang bangers, in this case, drug dealers, that sort of thing - but also routine enforcement because think about, for instance, the IRS. They don't say, OK, well, if you're not a money launderer, it doesn't matter whether you fill your tax return out right or not. They have both. They go after the really bad actors and they have a kind of general, routine enforcement.

But the question is - are we deporting a couple hundred people for show or are we actually making a serious effort to remove everybody who's got a final order of removal? When I say enforcement theater, what I mean is a kind of pretend enforcement.

But it's more an up-versus-down issue because the research has shown that opinion leaders, whether they're elected officials, journalists, business leaders - it's academics, religious leaders - they have dramatically different views on immigration. A

And they are much more skeptical of the very idea of having immigration limits, whereas the public - again, independents and Democrats, as well as Republicans, although not necessarily all in the same proportions - have a much stronger sense of the American government and American law having responsibility to Americans specifically rather than to people around the world. So the polarization is up versus down, not really right versus left.

Of 472 civilian occupations defined by the Department of Commerce, only six are majority immigrant (legal and illegal). These six occupations account for 1 percent of the total U.S. workforce. Many jobs often thought to be overwhelmingly done by immigrants are in fact majority native-born: 51 percent of maids are U.S.-born, as are 63 percent of butchers and meat processors, and 73 percent of janitors.