Cities are, of course, in constant flux and new forces come into play in shaping their continued development. The populations of the Earth are not in equilibrium: they are rapidly expanding, their ethnic and cultural make-up is rapidly shifting, the distribution of wealth is becoming more uneven, technology is advancing, and populations are on the move at least as much as they ever were, transport methods and commuter patterns change, economics is unstable and in constant flux, political motives and methods change and then there is globalization. Cities are strained and struggling to adapt. Newer models, for cities in the MEDW (more economically developed world) at least, attempt to factor in economic deindustrialization and the rise of the service and technical industries, the reliance on the automobile, and urban planning.
Since the publication of the three classical models of urban land use many new forces have come to influence urban growth. These reflect societal changes such as the deindustrialization of the urban economy, the emergence of a service economy, the dominance of the automobile, a decrease in family size, suburban residential developments, decentralization of business and industry, and increased intervention by the government in the process of urban growth. White (1987) proposed a revision of the Burgess model that incorporates these trends in order to guide our understanding of the twenty-first-century city.
The model comprises seven elements Core. Zone of stagnation. Pockets of poverty and minorities . Elite enclaves. The diffused middle class. Industrial anchors and public sector control. Epicentres and corridors.
E = ethnic enclave, I = institution (university, R&D centre or business park, hospital, etc.), MC = middle class (orange areas), B lue indicates areas of poor housing, Red areas indicate areas occupied by the city's 'elite' .
Core : The CBD remains the focus of the metropolis. Its functions may have changed over the years but it still houses the major banks and financial institutions , government buildings , and corporate headquarters as well as the region’s main cultural and entertainment facilities . A few large department stores retain flagship establishments downtown , but most retailing has moved with the affluent population to the suburbs, with many remaining outlets being specialty stores catering to daytime commuters . Zone of stagnation : Burgess expected investors from the CBD to expand into the zone in transition , White depicts the area as a zone of stagnation . He argues that rather than extending outwards spatially, the CBD expands vertically . The lack of investment in the zone was compounded by the effects of slum clearance, highway construction, and the relocation of warehousing and transport activities to suburban areas.
Pockets of poverty and minorities: These comprise highly segregated groups living on the fringes of society, including the homeless, addicts, dysfunctional families, the underclass, and members of minorities . Many of these areas surround the stagnation zone and may constitute modern 'slums '. Elite enclaves : The wealthy have the greatest choice of housing environment and are able to insulate themselves from the problems of the metropolis. Most live in neighbourhoods on the urban periphery in expensive houses on spacious lots. The diffused middle class. The middle class is diffused, spreading to occupy most of the city metropolis. Generally, those closest to the core are older areas occupied by those of lower socio-economic status (SES).
Ethnic groups, historically of lower income, originally dominated the areas closest to the core, but are now moving outwards to the suburbs, but remain segregated in their own enclaves. The more affluent middle classes live in better and newer accommodation in the suburbs . Industrial anchors and public sector control: Industrial parks, universities, R&D centres, hospitals, business and office centres, corporate headquarters and other large institutional property holders can exert a major influence on patterns of land use and residential development. Institutional actors and other members of a local growth coalition can pressure city government to modify zoning, lower taxes and construct infrastructure. The location of such activity (e.g. the siting of a large shopping mall) is of considerable importance in shaping the urban structure.
Epicenters and corridors: Epicenters are commercial centres which have taken over many of the functions of the old CBD and are generally sited where main highways converge or develop as corridors along main transport routes.