raw materials, to refining those materials into more sophisticated products, to vari-
ous levels of services that require some skill, from the relatively simple (the shin-
ing of shoes) to quite complex (research and development of a new cancer-fighting
drug). An emerging school of scholars argues that yet a fifth sector must now be
considered: the quinary sector. This school of thought holds that there are “hid-
den” economic activities of considerable value that remain unaccounted for in
the traditional four-sector model. These include non-profit activities and public
services funded by governments, such as police and fire protection, public educa-
tion, and others. In addition, domestic work performed by homemakers, activity
that typically does not generate profit but has value and is ubiquitous, is also con-
sidered by many economists as belonging to the quinary sector. In some cases it is
difficult to assign a monetary value to the quinary sector, because the “products”
of this sector are not necessary subject to the law of supply and demand, yet many
economists have come to recognize that economic value and output do not always
conform to market dynamics.
Segregation
The spatial division of apopulationaccording to racial or ethnic characteristics.
Since the 1950s many studies in social geography have been conducted on the res-
idential racial segregation present in most major cities in the United States. Before
the 1920s, many cities in the northernregionof the United States had a relatively
small black population, but a largemigrationof Southern blacks in the 1920s and
1930s northward greatly increased the percentage of African Americans living in
urban places like Detroit, Chicago, Milwaukee, Cleveland, and New York. By
the 1950s sociologists of the so-called “Chicago School” were conducting
research on the spatial separation of racial groups in Chicago, and this research
stimulated similar studies of the racial segregation patterns found in other cities.
Segregation in residential areas in these urban environments followed more or less
the same geographical arrangement—an inner city that was predominantly black,
with smaller clusters of other ethnic or racial minorities; and a surrounding fringe
of suburbs that were overwhelmingly populated by white residents. In the 1960s
these spatial patterns appeared to become even more distinct, and were accompa-
nied by a decline of the inner-city area. Property values declined, the local tax base
eroded, and the quality of services provided to residents suffered, including law
enforcement, fire protection, and education.
The term “white flight” was coined to describe the process whereby cities
became racially segregated. Whites began leaving inner-city neighborhoods in the
Segregation 305