There are so many things I don't know. For instance: how many people could read Latin in the Roman Republic and Empire, and then in Western Europe after the fall of the Western Empire? We tend to assume that the numbers dropped drastically between the Classical era and the Dark Ages, but is this true, or is it more the case that a large illiterate demographic of Germanic peoples are more prominent in our backward historical gaze, while the actual Romans remained as literate as before, although less powerful?
Has the total number of people at any given time who could read Latin ever been in the millions? Has the number actually declined over the past couple of centuries, or does it only seem smaller because it represents a smaller percentage of the much greater number of people who now have attended universities?
For some works of Classical Latin there have survived hundreds of manuscripts, some have disappeared, perhaps never to be recovered, some are represented today by a single manuscript. Does the number of manuscripts known to us today tell us anything about the past popularity of a given text? I wonder. Books xli-xlv of Livy's ab urbe condita, his history of Rome from its mythical beginnings down to his own time during the reign of Augustus, appeared to have vanished when in 1527 Simon Grynaeus found them in a 5th-century codex in a monestary in Switzerland. Before 1527 30 of Livy's 142 books -- think of books of the Bible, Livy's books are of a roughly comparable length -- were known to the public, since Grynaeus' discovery it's been 35, plus a few small fragments which have since come to light here and there, and two compilationd from the 4th century AD, an anonymous summary or periochae, and a listing by a certain Julius Obsequens of all the "prodigies" -- natural disasters, plagues, eclipses and so forth -- mentioned in the entire work. And yet the mentions of Livy in other ancient, medieval and modern texts seem to indicate that he was consistently one of the most highly-regarded, widely read of all Classical authors.
But that's yet another speculation on my part, inferring a rough idea of the comparative size of dimensions of Livy's total readership based on some comments here and there. For all I know, some other writers in ancient Rome could've been much more popular than Livy, writers about whom no-one today knows anything, because the interest in them died out quickly, and the people who may have written mentions of them were themselves not considered interesting, and so their writings too were lost. A lot can get lost in 2,000 years, lost or destroyed or forgotten. Or just misplaced, like that 5th-century copy of Livy's books xli-xlv. The volume may have lain on that shelf in that monastery in Switzerland for centuries without so much as being touched.
How many other interesting old manuscripts are just laying around, with a race going on, a very very slow race between someone eventually finding them, by design or accident, and them rotting away?
Again: I really have no idea at all. I'd like to see Livy's work restored to its full 142 books. I'd love to discover some of the missing material myself, but there's an entire branch of a learned profession in line in front of me in terms of being likely to make such a find. How likely is it that anybody will ever find anything more of Livy's work?
Again: I. Really. Just. Don't. Know.
The authors of the anthology Texts and Transmission, ed by L D Reynolds, are very bright and learned, and have much more exact ideas about the possibilities and probabilities involved in such things than I.