Malthus' wrong predictions did not deter Stanford University professor Paul Ehrlich from making a similar prediction. In his 1968 best-seller, "The Population Bomb," which has sold more than 2 million copies, Ehrlich warned: "The battle to feed all of humanity is over. In the 1970s and 1980s hundreds of millions of people will starve to death in spite of any crash programs embarked upon now." This hoax resulted in billions of dollars being spent to fight overpopulation.

According to the standard understanding of the term, human overpopulation occurs when the ecological footprint of a human population in a specific geographical location exceeds the carrying capacity of the place occupied by that group. Let's look at one aspect of that description — namely, population density. Let's put you, the reader, to a test. See whether you can tell which country is richer and which is poorer just by knowing two countries' population density.