In the table below, column one shows regional illiteracy rates for people under the age of 65, which are nearly the same throughout Italy. Column two shows people 65 and over, where the gap still persists. And column three shows the total population. The data was compiled by Istat for the 2001 census.
Vincenzo D'Aprile. "Analfabetismo: Italia — Censimento 2001: Cinque Grandi Ripartizioni Geografiche e Venti Regioni". Educazione&Scuola, 2005.
*According to Felice and Giugliano (2011): "The reason literacy was so low in the Southern regions was that, until 1861, they formed a different state, the Kingdom of the Two Sicilies, which did not promote compulsory education, unlike the pre-unitarian states of Northern Italy. Once compulsory education was extended to the South (from 1861) and after adequate financial resources were spent for its provision by the Italian State (from 1911), the Southern regions converged in literacy."