The physical environment and social well-being of central cities depend largely on employment opportunities, a rising tax base, and income distribution. Unskilled immigrants are an increasing proportion of the urban population, and the decreasing number of jobs available to them means they rely on government for welfare, medical care, housing, food, and other essentials. At the same time, the ability of central cities to provide these services is hampered by the continuously declining tax base resulting from the suburbanization of industries and the movement of the middle class away from city centres.
The assimilation of newcomers into urban areas has to be assisted by the inhabitants already there, who must nevertheless compete with those they help for the same unskilled or semi-skilled jobs. The friction thus engendered is compounded in the current situation by the existence of prejudice against minority groups. Largely middle-class populations have felt their property and person to be threatened by peoples of a different colour or ethnic group, and have moved to the suburbs, where they now defy others to follow. What used to be a socially and ethnically diverse population living in districts or 'villages' within the central areas of cities has become a more homogeneous population consisting mainly of less educated minority groups often demoralized by their lack of occupational opportunities, by substandard housing conditions, and by the general deterioration of living conditions in the city centre. Even where actual prejudice does not exist, cultural and educational differences stimulate urban middle-income families to seek out suburban neighbours like themselves.