Earlier today I was on a segment of Al Jazeera’s talk show, “The Stream,” discussing political polarization, social media’s role in promoting it, and possible ways to combat it.

My view in a nutshell: just as social media has enabled previously isolated people to find kindred spirits, and hence has fostered new communities and a new sense of belonging, it has made it easier to live in an informational bubble in which you only hear from the like-minded. But I don’t think this is anything more than a surface layer on top of something much deeper. We are increasingly polarized because of social, economic and political trends that have developed over 30-50 years, from the ideological sorting of the parties (and the distinct problems that sorting creates for our political institutions, which depend on a certain level of cross-partisan comity to function properly), to the rise of alternative conservative media, to globalization and the consequent deindustrialization of America and rise of a transnational elite, to . . . well, it’s a long list. And it’ll take a lot more than a cute app to counteract all that.

One point I didn’t make forcefully enough on the program is that we are increasingly polarized in the real world, not just on line. It’s not just that conservatives and liberals only talk to the like-minded, or that we’re all spending so much time on line that we don’t encounter people in meatspace anymore. It’s that increasingly we only live near the like-minded, politically-speaking.

David Wassermam at Fivethirtyeight.com has a very sobering piece on the subject up today, that is well worth a read:

Of the nation’s 3,113 counties (or county equivalents), just 303 were decided by single-digit margins — less than 10 percent. In contrast, 1,096 counties fit that description in 1992, even though that election featured a wider national spread.1 During the same period, the number of extreme landslide counties — those decided by margins exceeding 50 percentage points — exploded from 93 to 1,196, or over a third of the nation’s counties.

Sure, it’s people who vote, not counties — and it’s not quite fair to give equal weight to Los Angeles County, California (pop. 10 million, 76 percent Clinton), and Loving County, Texas (pop. 112, 94 percent Trump). But a more equitable way to measure this “big sort” is to track the share of all American voters living in polarized communities over time. And 2016 was off the charts (figuratively speaking; it’s on the chart below):

The electorate’s move toward single-party geographic enclaves has been particularly pronounced at the extremes. Between 1992 and 2016, the share of voters living in extreme landslide counties quintupled from 4 percent to 21 percent.

And remember, this was in a year that, like 1976, scrambled what we think of as the usual party coalitions, with the Democrat doing better than usual in states like Texas and Georgia and the Republican (more significantly) doing better than usual in states like Wisconsin and Pennsylvania. In other words, what on the surface may have looked like an electoral reshuffling was actually a deepening of prior trends turning us into an ideological archipelago of single-party islands.

All of which does not bode well for the future:

In an increasing number of communities like Baldwin County, Alabama, which gave Trump 80 percent of its major-party votes, and San Mateo, California, which gave Clinton 80 percent, an entire generation of youth will grow up without much exposure to alternative political points of view. If you think our political climate is toxic now, think for a moment about how nasty politics could be 20 or 30 years from now.