Holds that in an ideal (or model) urban hierarchy, the population of a city or town will be inversely proportional to its rank in the hierarchy. For example, if the largest city has 12 million people, the second largest will have about 6 million (1/2) and the third will have 4 million (1/3). So n= the population ranking and the ratio will be 1/n. This leads to evenly spaced cities which provides services for the population in a somewhat uniform way.