33 questions is sort of the Shannon-Hartley optimal encoding of identifying information about human beings. That means to come up with them is identical to fin

33 questions is sort of the Shannon-Hartley optimal encoding of identifying information about human beings. That means to come up with them is identical to finding an optimal compression of identifying data. Necessarily, as the second question already implies, for this question to correctly divide the population in half, you would have to group large amounts of small populations together, resulting in very long questions. For example, if you'd like to make another geographical question that's independent of the second one, it would have to divide in half every population of the 6 countries you mentioned. The next question would necessarily have to divide those 12 again. By the way, the first question you ask is already suboptimal when combined with the second question, as those countries together probably do not have a clean 50% male/female split. (if they do, you should really explain that as it's not obvious)