concentric zone theory A diagram of the ecological structure which, in the words of its author, ‘represents an ideal construction of the tendencies of any … city to expand radially from its central business district’ ( R. Park and and E. Burgess , The City, 1925)
. The theory posits concentric zones round the central area, defined by their residential composition, moving from the very poor and socially deviant, in the inner zone of transition, to a peripheral suburban commuter ring.

Burgess himself argued that this structure is the result of competition between users for land—a process analogous to the ecological competition between biological species for territory. In human societies, these ‘biotic’ processes are overlaid by cultural processes, which limit the conflict and social disorganization resulting from unfettered territorial competition. Control is exercised through the division of the population into distinctive groups, defined by common ethnic identity, occupational status, or economic position. Within each zone, groups occupy particular natural areas, so forming an ‘urban mosaic’ of local communities. Social and economic mobility cause changes in the pattern of territorial occupation, via the ecological processes of invasion, domination, and succession.

This model is an ideal type. However, geographers and economists subsequently proposed more complex diagrams of urban structure and typologies of the natural areas, aided by the advent of large data-sets and computer technology. This social area analysis largely ignores the wider issues of social process and structure which concerned Burgess and his colleagues in their distinctive contribution to the development of urban sociology. See also CHICAGO SOCIOLOGY; HOUSING CLASS; INVASION–SUCCESSION MODEL; URBAN ECOLOGY.