There is a much more complicated one as well, which compares the statistics ( such as the early ones are ) from about 1955 through to date and demonstrates the functional rate of illiteracy ( as opposed to literacy) has slightly declined over the years, as I indicated mainly reducing between 1997-2005, and then slightly widening form 2008-2011 the last set of definite statistics. I have presented that demonstration previously on this site, I think in response to a query some time ago by maybe another Lurker, however, tonight the search engine on this forum steadfastly refuses to produce the reference!