It cannot be a sign of social health that the number of tweets per day worldwide exploded from 5,000 in 2007 to 500 million six years later. And this might be related, by a few degrees of separation, to the fact that whereas in the 1992 presidential election more than one-third of America’s 3,113 counties or their equivalents had a single-digit margin of victory, in the 2016 presidential election, fewer than 10 percent did. And to the fact that in 2016, 1,196 counties — about 2.5 times the average over the preceding 20 years — were decided by margins larger than 50 percent. All of which are perhaps related to rising skepticism, without scientific warrant, about the safety of vaccinations and genetically modified foods. And to the fact that newspaper subscriptions have declined about 38 percent in the past 20 years. And that between 1974 and 2016, the percentage of Americans who said they spent significant time with a neighbor declined from 30 percent to 19 percent.