It is commonly observed in OECD (Organisation for Economic Cooperation and Development) countries that unemployment is unevenly distributed among cities. The incidence of unemployment varies between the regions of a country (Isserman, Taylor, Gerking, and Schubert, 1986; Gordon, 1987; Blanchflower and Oswald, 1994), cities of different sizes and functions (Marston, 1985), inner and outer areas of cities, and between urban and rural areas. There are also stark spatial differences in incomes. For example, in the United States, the median income of central city residents is 40 percent lower than that of suburban residents. This has renewed interest in the spatial dimension of unemployment and, more generally, of the labor market.

According to the U.S. Bureau of the Census, in large U.S. cities, the unemployment rate is much higher in the city center than in the suburbs. This is, in particular, due to the fact that U.S. city centers are generally characterized by ghettos and poverty. Even if the European situation is more complex and less uniform, the general tendency is similar – but opposite. Indeed, poor and unemployed workers tend to reside on the outskirts of the city while rich workers tend to live close to the city center. The spatial concentration of unemployment and poverty makes the workings of urban labor markets a vital concern for urban residents.

The labor market is therefore not a global market in which the labor force is homogeneous. Quite the opposite. There is an increasing heterogeneity of the labor force as well as a thinner segmentation of this market into submarkets characterized by a fairly weak mobility between segments.