It's a piece written deliberatley to proove his point. For instance, //"If for each question I wrote each of the possible alternatives on bananas, and asked chimpanzees in the zoo to pick the right answers, and by picking the right bananas, they'd just pick bananas at random. But the Brits did even worse," says Rosling.//
The monkeys cannot read and would not try to analyze the figures, they simply pick random figures. It proves nothing at all.
Secondly you may not agree with some of the figures, after all they are simply one bodies estimate and may well be scewed to prove their point.
In short I wouldn't be bothered if you only got three.