It is hard to tell what percentage of the population in the tiny Kingdom of Judah – whose population numbered just around 100,000 – could read and write, Finkelstein said. But the fact that one of the Arad letters was penned by Eliashiv’s deputy means that literacy trickled down to the lower levels of society. It is unlikely that a member of a leading family would be given such a relatively lowly post in a remote desert fort, he said.It's difficult to evaluate the results of this project based only on a few popular articles that are in turn based on a press release. I would rather have the final publication, but all in good time. Overall, it sounds reasonably persuasive. It was pretty clear already from the epigraphic evidence that literacy was widespread by the late 7th and early sixth centuries BCE (i.e., roughly the reign of King Josiah). For example, an officer writing one of the Lachish letters (letter 3) was insulted that his commanding officer implied that he couldn't read.
"We found indirect evidence of the existence of an educational infrastructure, which could have enabled the composition of biblical texts," said Piasetzky. "Literacy existed at all levels of the administrative, military and priestly systems of Judah. Reading and writing were not limited to a tiny elite."
On the other hand, Finkelstein noted: "Following the fall of Judah, there was a large gap in production of Hebrew inscriptions until the second century BCE, the next period with evidence for widespread literacy. This reduces the odds for a compilation of substantial Biblical literature in Jerusalem between ca. 586 and 200 BCE.”
That said, the study draws some broad conclusions based, first, on a very small sample of evidence and, second, on an argument from relative silence. So some caution is in order. I look forward to seeing the final publication with a fully detailed account of the evidence, analysis, and arguments.