Saint-Exupery's account of Earth, especially the statistics he relays in both Chapters 16 and 17, actually fits in with one of the most dominant themes of the book. In addition, the irony found in these descriptions also adds a great deal of humor.
The most dominant theme in the book is materialism and its consequences. In Chapter 17, it becomes very evident how Saint-Exupery's recitation of Earth's statistics fits in with the theme of materialism. Here he states that he was exaggerating in the previous chapter. The exaggeration is seen in his idea of lamplighters lighting entire continents in sequence, just like a dance. The truth is that entire continents would never be lit up because in reality, mankind does not occupy the entire Earth, only "a very small place upon the Earth." He further points out that all two billion people inhabiting Earth could actually all stand together on one "small Pacific islet," just as they would in a stadium. He further argues that most people would actually not believe that all of Earth's inhabitants can occupy a small space. Instead, "They imagine that they fill a great deal of space."
Which brings us to the heart of his argument. Mankind is so caught up in numbers and figures and so vain that "they fancy themselves as important as the baobabs" (Ch. 17). In other words, Saint-Exupery is using his statistics of Earth to prove mankind's arrogance and to show that mankind is caught up in materialism. The figures actually represent materialism because they are all figures of material objects. All of the figures he quotes in Chapter 16, including the 111 kings and the two billion grown-ups is to make the reader reflect on his or her own self-importance and to make the reader get caught up in the figures in order to prove in the next chapter that mankind is indeed arrogant and caught up in materialism. Hence, the use of the statistics serves to prove his point that mankind is interested in large numbers and therefore materialistic.