That's intentionally misleading and it's thrown around frequently without clarification of what the basic and below basic levels exactly mean, how they compare to the rest of the world, and who is in the figures (a lot of non-English speaking immigrants), usually to try to prove points.
The US basic literacy level is a high bar compared to what 95% of the planet actually tests at. Over half of China is below basic by the US standard. Over half of Eastern Europe is below the US basic line, including Russia.
In the US ~44% of the below basic population are non-native English speakers, who didn't speak English at all prior to starting school. 39% are Hispanic adults. Ie this group overwhelmingly consists of currently or originally low skill, poor immigrants (people that wouldn't even be allowed into most other developed nations such as Canada).
Demonstrating that effect in action, 43% of hispanic adults test poorly in literacy, compared to about 10% of white adults. Gee, I wonder if immigration into a new culture + language barrier has something to do with these numbers.
Despite a vast immigration flow of low skill, poor, low English literate persons since 1980, the US literacy rate didn't drop meaningfully. That means literacy rates for the base population increased.
Despite all of that, the US is the 7th most literate nation on earth, in front of: Canada, Germany, the Netherlands, France, New Zealand, Belgium, Israel, South Korea, Italy, Ireland, Russia.
https://www.washingtonpost.com/news/answer-sheet/wp/2016/03/...
Americans are well educated relative to the global population. That isn't what we're discussing. OP is explaining why large swaths of the population might prefer communicating with pictures over words. It isn't that they can't understand words. Just that parsing and constructing language to express complex thoughts isn't a common experience for many, for whatever reason. Emojis fill that gap.
In a globalised world, a great many people are frequently communicating in a language that they have not fully mastered. South Africa has eleven official languages. India has 22. Globally, non-native English speakers outnumber native speakers by two-to-one. Hindi/Urdu has a roughly equal number of first and second language users.
But as for deciding it exists because people aren't smart enough to use words, U+1F914.
(I know this thread isn't about the methodology of literacy assessment, but now I'm really curious to know how they do it. Does publicly available question-level response data exist somewhere out there? from previous years?)
In the last National Assessment of Adult Literacy, 43% of Americans were assessed as having "basic or below basic" literacy. They can extract basic factual information from short, straightforward texts, but little more than that.
Here are a couple of example questions from that test.
Only 33% of Americans could describe what is expressed in the following poem:
"The pedigree of honey Does not concern the Bee - A clover, any time, to him Is Aristocracy"
Either a literal or thematic description of the poem constitutes an acceptable answer.
Read the text at the link below. After reading this text, only 16% of Americans could describe the purpose of the Se Habla Español expo.
https://nces.ed.gov/NAAL/sample_imgtxtequiv.asp?Imageid=164
Acceptable answers include any statement such as the following: "to enable people to better serve and sell to the Hispanic community", "to improve marketing strategies to the Hispanic community" and "to enable people to establish contacts to serve the Hispanic community".
Did you get the right answer? 84% of Americans didn't. Bear that in mind when you're writing documentation or dialog boxes.
https://www.nngroup.com/articles/writing-for-lower-literacy-...