I'm not sure that caption is quite honest. Clearly, not everybody in the world can read that English caption. However, for three billion people in the world to be illiterate, 44.2% of all people worldwide would have to be illiterate (or, in other words, the world would have to have a literacy rate of 55.8%). Only 20 out of the ~204 countries in the world have a literacy rate less than or equal to 55.8%, and their total population is ~467 million. That's a large number, but that's less than a tenth of the world population. Plus, even if you wanted to say that it referred to English exclusively for some reason, there are 760 million people in the world who speak English - also a far cry from the number of 3 billion who don't.
Don't get me wrong, I understand exactly the message that the author is trying to get at. It's just that there are plenty of things wrong with the world that accurate numbers will still clearly show.
(Plus, I'm playing around with Mathematica 8, and it has built in Wolfram Alpha references. I just had to try this.)