“Every society has some group of people—somewhere between a minuscule amount and half the adults—that read a lot in their leisure time,” says Wendy Griswold, a sociologist at Northwestern University who studies reading. Griswold refers to this group as “the reading class,” and—adding up the NEA’s “frequents” and “avids,” and considering rates of serious reading in other similarly wealthy countries—reckons that about 20 percent of adults belong to the U.S.’s reading class. She said that a larger proportion of the American population qualified as big readers between the mid-19th and mid-20th centuries—an era of reading that was made possible by advances in printing technology and then, eventually, snuffed out by television.

Some people are much more likely than others to become members of the reading class. “The patterns are very, very predictable,” Griswold told me. First, and most intuitively, the more education someone has, the more likely they are to be a reader. Beyond that, she said, “urban people read more than rural people,” “affluence is associated with reading,” and “young girls read earlier” than boys do and “continue to read more in adulthood.” Race matters, too: The NEA’s data indicate that 60 percent of white American adults reported reading a book in the last year outside of work or school, which was a higher rate than for African Americans (47 percent), Asians (45 percent), and Hispanic people (32 percent). (Some of these correlations could simply reflect the strong connection between education and reading.)

Of course, possessing any of these characteristics doesn’t guarantee that someone will or won’t become a reader. Personality also seems to play a role. “Introverts seem to be a little bit more likely to do a lot of leisure-time reading,” Daniel Willingham, a professor of psychology at the University of Virginia, told me.

Willingham also talked about the importance, which many researchers have examined, of the number of books in one’s childhood home. Studies looking at “family scholarly culture” have found that children who grew up surrounded by books tend to attain higher levels of education and to be better readers than those who didn’t, even after controlling for their parents’ education.

The mere presence of books is not magically transformative. “The question is, I take a child who’s not doing very well in school, and I put 300 books in their house—now what happens?,” Willingham said. “Almost certainly the answer is, not a lot. So what is it? Either what are people doing with those books, or is this sort of a temperature read of a much broader complex of attitudes and behaviors and priorities that you find in that home?”

It is almost tautological to observe that being a reader sets a child up for academic success, since so much of school is reading. And that means-to-an-end argument in support of reading says nothing of the many joys it can bring. But even though plenty of people simply don’t enjoy reading (or have trouble enjoying it, possibly because of a learning or attention disorder), it’s a vital skill. It may be dispiriting that people have little, if any, say over many of the predictors of whether they or their children will be readers, but thankfully, there are also a number of other factors that are within people’s control.