Now let's look at the productivity of the world's least productive 80%.
a. How much GDP do they produce? (Hint: You've already calculated this number in the previous question.)
b. What is the average GDP per capita of the least productive 80% of the world's population?
c. Now, the payoff: How productive is the average person in the top 20% compared with the average person in the bottom 80% of the planet?
Answer this by dividing your answer to question by your answer to question. This chapter and the next are devoted to explaining why this ratio is so large.