The Rank Size Rule is one of the most significant concepts in Population and Settlement Geography used to explain the distribution of city sizes within a country or region. It states that the population of a city is inversely proportional to its rank in the urban hierarchy. According to this principle, the second-largest city will have half the population of the largest city, the third-largest city will have one-third of the population of the largest city, and so on. This relationship provides an ideal pattern of urban settlement distribution and indicates a balanced system of urban development. The Rank Size Rule was first proposed by German geographer Felix Auerbach in 1913 and was later refined and popularized by George Kingsley Zipf in 1949 through his Principle of Least Effort. Zipf formulated the mathematical expression: Pr = P1 / r Where: * Pr = Population of the city of rank *r* * P1 = Population of the largest city * r = Rank of the city For example, if the largest city has a population of 10 million, the second-ranked city should have approximately 5 million people, the third-ranked city around 3.33 million, and the fourth-ranked city about 2.5 million. The Rank Size Rule reflects a