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The Distribution of Users’ Computer Skills: Worse Than You Think (2016)
(www.nngroup.com)
This is a most excellent place for technology news and articles.
I think it's a mix of all of these things.
Being able to read isn't quite equivalent to reading comprehension though. So between that, and lack of curiosity, laziness, defeatism, and more; it really does stunt the population when it comes to computer knowledge.