The components of comprehensive immigration reform proposals are broadly popular. Public opinion polls show pretty enduring support for both a path to citizenship and greater enforcement. But this consensus breaks down a bit when you look at age cross-tabs, where the young (18-29) seem to be significantly more accepting of immigrants than people over 50 — somewhat more supportive of legalization, and somewhat less supportive of enforcement measures. Here’s an example from 2010:

There’s a 19-point gap between the 18-29 group and the 50-64 group on all of these enforcement questions. This is typical of pretty much any numbers you’ll see on this.

This is interesting, because at the same time it’s being discussed how much baby boomers’ attitudes have changed over time on issues like gay marriage, drifting in the direction of the views of younger people. (Though such an argument may be overstated.) On immigration, though, baby boomers’ attitudes continue to look much, much more like those of the 65+ group than they look like those of young people.

Tying this in to the discussion about the historical levels of immigration to the United States, our all-time highs were around 15 percent, and our current level is around 13 percent. Considering how we’re a nation of immigrants, one may assume that this has stayed pretty steady throughout the 20th century. But instead, there was a huge drop-off in how much of the U.S. population was foreign-born in the middle of the century, and the size of this drop-off may surprise:

In 1950, the U.S. population was only 6.8 percent foreign-born — about half of what it is today. This number fell even more during that decade, so that only 5.4% of the U.S. populations were immigrants in 1960. By 1970, this bottomed out at 4.8% — fewer than one in twenty people. The Immigration and Nationality Act of 1965, though, had already been passed, and would broaden the scope of legal immigration (especially from Asia) hugely, thus helping create the demographic America we see today.

But this demographic America wasn’t the one of the baby boomers’ childhoods. Young people today are likelier to be used to an environment with a diverse number of sizable immigrant groups, but the baby boomer generation largely did not grow up with this. The conservative, nostalgic idea that there was once a simpler, white-bread America isn’t an idea I’m sympathetic to, because America has been an inherently multicultural enterprise since the early moments when first European settlers encountered North America’s native peoples. But in one sense, things really have changed in the past fifty or so years, in a way that may help explain a seemingly enduring generation gap on immigration.