Nationally over 20% of adult americans have a literacy proficiency at or below Level 1

so first of all "nationally" is redundant, so don't jot that down.
Secondly: 1/5 of adult americans can't read AT ALL?? That's... that's too much.

Christ that page needs and editor

The definition of literacy has changed greatly; the term is presently defined as the ability to use printed and written information to function in society, to achieve one's goals, and to develop one's knowledge and potential

Add quotation marks ffs

Modern jobs often demand a high literacy level, and its lack in adults and adolescents has been studied extensively.

Not really relevant to the discussion of literacy in the US. Certainly not in the introduction.

According to a 1992 survey, about 40 million adults had Level 1 literary competency, the lowest level, comprising understanding only basic written instructions.

You are adding it as a source, just write the claim and add the year the claim was made.

A number of reports and studies are published annually to monitor the nation's status, and initiatives to improve literacy rates are funded by government and external sources

Should be the first sentence if you're going to include it at all.