Central Places Theory (Market Principle)
Central places theory is deri from the work of the German
geographer Walter Christaller who investigated the urban system of Southern
Germany during the 1930s. He was mainly looking for relationships
between the size, the number and the geographic distribution of cities.
Although his work is mostly empirical, it is the theoretical part
that had the most impacts on geography. His observations enabled
the elaboration of this important theory of spatial structure and order, mandatory
in the study of urban, economic and transport geography.
Central places theory tries to explain the spatial
distribution of a system of cities. This distribution is best understood by
assuming a central place
and its market area. A central place has the main function to supply
goods and services to the surrounding population. It is specialized in selling various
goods and services, and the market area is the summation
of consumers traveling to the central place, which is a part of hierarchy
with other central places. Its influence
is a function of its market area and the size of this market area
will determine the nature of the spatial order. The above figure
illustrates a system of central places according to the market
principle with three orders of centers. In this case the market
area of a center of higher order includes the equivalent of
three market areas of centers of the next lower order.
Central place theory, as a model of the regional spatial structure, has
been the subject of numerous criticisms. The basic hierarchical
rules can be questioned, partly because the theory relates only to the service sector.
Settlements may develop due to other factors such as the
availability of natural resources. The Christaller model holds such factors
constant assuming an even plain and a uniform distribution of natural
resources. As such, central place theory cannot provide an all-inclusive
general theory and there is a need to introduce other theories to explain
agglomerations in many areas. The theory also assumes a uniform
distribution of the population. This rarely occurs in practice since factors
such as soil fertility and climate vary and
distort the spatial structure. Also, the dominance of a large
metropolitan center may create a "shadow effect", inhibiting the growth of smaller centers
Still, central place theory is probably the most researched and well-known
model of the regional urban spatial structure. It is
a purely deductive theory of a highly simplified and abstract nature
developed on the basis of very idealized assumptions. It relates only
to the service element of regional economy, failing to explain distortions
in the hierarchy caused by the location of primary and manufacturing
industry, which tends to group into cluster or agglomerations due to
resource location. The theory is essentially static, explaining the
existence of a regional spatial structure but failing to explain how
that structure has evolved in the past and might change in the future.
Still, it serves a useful role at identifying important concepts such as the interdependence
of a city and its region, a hierarchy of functions and centers, and
range and threshold populations.