What is the rank size rule?

The rank size rule is a pattern observed in urban populations where the size of a city is inversely proportional to its rank in the hierarchy of cities within a country. In other words, the largest city in a country will be approximately twice the size of the second largest city, three times the size of the third largest city, and so on.

This phenomenon was first described by the economist George Zipf in the 1940s and has since been studied extensively in urban geography and economics. The rank size rule suggests that urban systems tend to follow a fractal distribution, with a few very large cities dominating the urban landscape while the majority of cities are much smaller in size.

The rank size rule is a useful tool for understanding urban hierarchies, population distribution, and economic development within a country. It can also be used to predict the size of cities within a country based on the size of its largest city. However, the rule does not hold universally true for all countries and regions, as factors such as historical development, political decisions, and natural resources can influence the size and distribution of cities.