The definition has probably changed over time. I doubt many people in the US or here cannot read STOP, or GIVE WAY, or the names of their street and town as they are plastered all over the place compared to 1910. MacDonalds, Fox, Trump, even Kardashian are probably not beyond 99% of the population. But knowing how education statistics are usually skewed to make the authorities look as good as possible (google Baltimore high school pass rates, e.g. https://www.educationdive.com/news/...0-students-proficient-in-math-reading/443155/) the basic level is probably pretty basic.
