[hydrox24]

For any others reading this, the _illiteracy_ rate is 23.1% in California according to the parent's source. This is indeed the highest illiteracy rate in the US thought.

Having said that, I would have thought this was partially a measure of migration. Perhaps illegal migration?

[Eisenstein]

The "medium to high English literacy skills" is the part that is important. If you can read and write Chinese and Spanish and French and Portuguese and Esperanto at a high level, but not English at a medium to high level, you are 'illiterate' in this stat.