Compare methods

	Concentric Zone Model	Urban Density Gradient Model
Field	Urban Studies	Human Geography
Family	Process / pipeline	Regression model
Year of origin	1925	1951
Originator	Ernest W. Burgess (Chicago School)	Colin Clark; Edwin Mills & Richard Muth (theory); Bruce Newling (quadratic form)
Type	Descriptive urban-ecology model of concentric land-use and social zones	Family of functional models of urban population density as a function of distance from the centre
Seminal source	Park, R. E., Burgess, E. W., & McKenzie, R. D. (1925). The City. University of Chicago Press. ISBN: 9780226646114	Clark, C. (1951). Urban population densities. Journal of the Royal Statistical Society. Series A (General), 114(4), 490–496.
Aliases	Burgess Model, Concentric Ring Model, Burgess Concentric Zone Theory, Urban Ecology Zonal Model	Urban Density Function, Population Density Gradient, Density-Distance Function, Monocentric Density Model
Related	4	4
Summary	The concentric zone model, formulated by sociologist Ernest Burgess of the Chicago School in the 1920s, describes the city as a set of concentric rings of land use and social structure expanding outward from a central business district. Each ring — from the commercial core, through a transitional zone of factories and tenements, to successive rings of workers' homes, better residences, and commuters — represents a stage in the city's outward growth. Published in the 1925 volume The City, it was the first influential model of urban spatial structure and treated the city through the lens of human ecology, with zones competing and invading one another like species in an ecosystem.	The urban density gradient model is the broad family of functional relationships that describe how population density varies with distance from a city's centre. Its canonical member is Colin Clark's 1951 negative-exponential form, but the family also includes Bruce Newling's quadratic-exponential function that permits a density crater at the core, simpler linear and Smeed forms, and the economic micro-foundation supplied by the Muth-Mills monocentric city model. Together these give planners and economists a compact, comparable language for urban spatial structure.