What dose literacy mean in the demographics?

I wonder,what dose literacy mean?Can someone tell me if he knows?Thanks from now!

It's a measure of how many technologies that civ has researched, and is at 0% until you research Writing. I think when you have researched all techs it's 99%; even Future Tech does not change that. As far as I know all techs are worth one or two literacy points.

The formula if you have writing is # of techs / total # of techs * 100%, I think it truncates for display purposes.