>You misinterpret, the implication of quality is that having read a book is not indicative of value, someone could have a high metric "I read 10 books a year" but they're all short, low quality romance novels. Whereas someone could clam "I read no books a year" but they're a grad student with no time for novels.

I'd argue thataA grad student "with no time for novels" would still be if not functionality illiterate, at least uncultured, in my book (pun intended).

But that aside, such going "case by case", is not helpful. This is an aggregate statistics. If 50%+ of the population "didn't read a single book" this doesn't break down to lots of grad students with no time for reading or similar cases, but more like a major decline in functional literacy.

Having them reading "10 mediocre books a year" would have been a major improvement.