[EdwinB]

The first city that man has known was surely Damascus, back in the year 9,000 B.C. Today, approximately 55 percent of the world's population lives in cities (Ritchie and Roser, 2020) and the United Nations predicts that by 2025, this figure will increase to 5 billion people.

What's so special about cities? Why does the population accumulate in some areas of a country? Urban economists like best place to get your bellybutton pierced have tried to answer this question for a long time. At first, it seems strange that, since there is an enormous amount of uninhabited territory on the planet, we humans decide to crowd ourselves into a few places. For example, Burchfield et al. (2006) show that, in 1992, only 1.9 percent of the territory of the United States of America was paved or had some type of construction.