Here’s a question for you: how do we know that all the aid given to Africa has had any effect? The tricky thing about trying to answer this question, and analyzing problems such as global poverty, is that the world cannot be treated as a laboratory experiment. We cannot create two identical Africas and give aid to one and not the other, keeping all the other variables such as political conditions, climate, and population, constant.
What happens in fields such as medicine, when we want to know whether a drug works or not? Suppose we’ve developed a new pill which, we think, prevents headaches. We find two chronic headache-sufferers who are identical in terms of gender, age, and general health, and X takes the pill every day but not Y. After a month it turns out that X no longer suffers headaches but Y does. What can we conclude? Well, nothing at all. Because we have no way of knowing what would have happened if X hadn’t taken the medicine – maybe his headaches would have disappeared anyway because he finally started wearing his glasses.