In general usage, urbanization is associated with the concentration of population in towns and cities. There are, however, three linked concepts which are associated with urbanization. These are:
(i) Demographic phenomenon,
(ii) Structural change in society, and
(iii) Urbanization as a behavioural process.
As a demographic phenomenon, urbanization is interpreted as a process involving the absolute and relative growth of towns and cities within defined areas (usually a country).
This is often represented as taking place in two stages: first, an increasing proportion of the population is resident in urban places and second, the proportion living in the largest places increases.
The end of the sequence is presented as an almost completely urbanized society, with the great majority of its population living in a few large places.
Linked with the demographic process is the structural change in the society, consequent upon the development of industrial capitalism.
Cities are presented in the foci of the exchange processes that are central to this mode of production. With the latter, the search for increases in productivity led to the development of urban factories to reap the economies of scale and the advantages to be gained from the processes of concentration and centralization.
The third concept associated with urbanization is that urbanization is behavioural process. Urban areas, especially large cities, have been identified as centers of social change; attitudes, values and behaviour patterns are modified in the particular milieu of the urban place, characterized by its size, its density, and the heterogeneity of its inhabitants (urbanism) and then spread to the rest of the population by process of diffusion through the urban system.
In this expanded view of urbanization, the demographic component is presented as the dependent variable, the outcome of economic processes.
It is the structural component that provides the driving force, since it is the search for scale economies that leads to the need for cities in order of economic development to proceed.
The behavioral component is also in a secondary position in the model, with social change presented as an outcome of the creation of large cities.
The three components interact, e.g., demographic growth stimulates structural change through multiplier effects and behavioural changes attract immigrants, but the basis of urbanization is economic change and, in particular, the growth of large-scale production.
This model of urbanization has been challenged in recent years on a number of grounds, most of them relating to the central role of the growth of factory production.
First, it is pointed out that there were large cities in other parts of the world, notably Asia and Africa (Baghdad, Delhi, Patna, Lahore, Agra, Surat, Beijing, Shanghai, Damuscus, Jakarta, Cairo, and Alexandria), long before the Industrial Revolution.
Moreover, rapid demographic urbanization of North-West Europe: city growth is not dependent on the factory alone (Johnston, 1984; Taylor, 1986).
Second, in many of the more advanced countries, demographic urbanization has halted and the larger places are in decline: late capitalism does not necessarily require the continued concentration of population.
Third, in many of the less developed capitalist countries, the pace of demographic urbanization is far outrunning the pace of industrialization, and thus city growth is taking place without a central role for the factory. Demographic urbanization thus comes about for a variety of reasons as part of the structuring of space within a social formation; there is no reason to suppose that what is typical of one time and place is necessarily typical of others.