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	Rank-Size Rule	Central Place Analysis
Field	Human Geography	Human Geography
Family	Process / pipeline	Process / pipeline
Year of origin	1949	1933
Originator	George Kingsley Zipf	Walter Christaller
Type	Empirical regularity and diagnostic for the size distribution of cities	Theory and analytic framework for the size, number, and spacing of settlements
Seminal source	Zipf, G. K. (1949). Human Behavior and the Principle of Least Effort. Addison-Wesley, Cambridge, MA. ISBN: 9781614273790	Christaller, W. (1966). Central Places in Southern Germany (C. W. Baskin, Trans.). Prentice-Hall. (Original work published 1933). ISBN: 9780131226302
Aliases	Zipf's Law for Cities, Rank-Size Distribution, City-Size Rank-Size Relationship, Rank-Size Regularity	Central Place Theory, Christaller Central Place Model, Settlement Hierarchy Analysis, Central Place Hierarchy
Related	4	4
Summary	The rank-size rule is an empirical regularity describing the size distribution of cities within a country or region. In its simplest form, popularized by George Kingsley Zipf in 1949, the population of a city is inversely proportional to its rank, so the second-largest city is about half the size of the largest, the third about a third, and so on. Generalized to a power law with an exponent q, it provides a compact way to summarize how evenly or unevenly population is spread across a settlement system and to diagnose urban primacy.	Central place analysis is the study of the size, number, and spacing of settlements as service centres, grounded in Walter Christaller's central place theory of 1933. It explains why settlements form an orderly hierarchy — many small villages, fewer towns, a handful of cities — and why higher-order centres are spaced farther apart and offer more specialized goods, deriving the famous nested pattern of hexagonal market areas from two economic concepts: the range and the threshold of a good.