How literate was the ancient world? I'm particularly interested in the Romans, Greeks, and Egyptians in, say, the first few centuries BC. It's hard to find authors willing to give an explicit number, though sometimes ranges are given:
[It is] unlikely that the overall literacy of the western [Roman] provinces even rose into the range of 5-10%. 
In ancient Egypt levels of literacy were very low, less than one per cent. 
Most stick to descriptive terms:
a very small percentage [of Roman Britains were literate] 
But there is evidence that it was not too low, e.g. Vindolanda. So what is known for different cultures? I've read a (semi-)famous book on the subject---some kind of Classics prizewinner, focusing on pre-Roman and Roman Egypt, published maybe 8 years ago---but even that didn't often, if ever, give numbers. This is somewhat frustrating because I don't know what "a very small percentage" is. 10%? 1%? 0.1%? 0.01%?
Any reasonable information would be welcome. I'd be happy to split this further if there's enough information (4th century BC Romans, Athens in its Classical Period, etc.) but so far the information I have seen deals with all of these together (thousand-year periods across the entire Mediterranean).
- William Harris, Ancient Literacy, 1989, p. 272.
- Ellis Evans, Language Contact in Pre-Roman and Roman Britain, Aufstieg und Niedergang der römischen Welt II.29.2 (1983), pp. 949-987.