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	Clark Density Model	Central Place Analysis
Field	Human Geography	Human Geography
Family	Regression model	Process / pipeline
Year of origin	1951	1933
Originator	Colin Clark	Walter Christaller
Type	Empirical regression model of urban population density decline with distance	Theory and analytic framework for the size, number, and spacing of settlements
Seminal source	Clark, C. (1951). Urban population densities. Journal of the Royal Statistical Society. Series A (General), 114(4), 490–496.	Christaller, W. (1966). Central Places in Southern Germany (C. W. Baskin, Trans.). Prentice-Hall. (Original work published 1933). ISBN: 9780131226302
Aliases	Clark's Law, Negative-Exponential Density Model, Exponential Population Density Gradient, Clark Density Gradient	Central Place Theory, Christaller Central Place Model, Settlement Hierarchy Analysis, Central Place Hierarchy
Related	4	4
Summary	The Clark density model is the classic empirical description of how urban population density falls with distance from the city centre, formulated by the economist Colin Clark in 1951. It states that density declines exponentially outward from a central peak, so that plotting the logarithm of density against distance yields a straight line whose slope is the density gradient. This negative-exponential 'law' became the standard model of urban spatial structure and the empirical foundation for later monocentric-city theory.	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.