Complementarity
This is a concept utilized in economic and transportation geography that emerges
from the notions ofareal differentiationandspatial inequality. Complementar-
ity arises between countries or regions due to differences in resource allocation,
variations in levels of economic development, or advantageous relationships in
economic production. Because resources, labor, capital, and other economic fac-
tors are not evenly distributed across the surface of theEarth, some regions will
possess or produce goods that other regions need, and vice versa. That is, a country
orregionmay complement others in terms of its resource endowment and its eco-
nomic production. This complementarity forms part of the basis for spatial inter-
action, in that it provides the motivation for economic exchange—countries or
regions must form relationships with those that complement them to obtain the
goods and resources they need or desire. It should be emphasized that simply the
spatial occurrence of surpluses and deficits is not enough to result in complemen-
tarity between regions—a mutual desire and ability to satisfy the requirements of
supply and demand must be present. Furthermore, complementarity by itself is
insufficient to stimulate interaction between two or more places, as transferability
and the lack of an intervening opportunity must also be considered; but without
complementarity the other factors will not be relevant. It may be that complemen-
tarity exists between two regions due to thecomparative advantageone or both
have in regard to economic production and trade. In this instance, although both
regions in question produce the goods that are traded (at least initially), comple-
mentarity is achieved by both specializing in the production of commodities in
which they hold a relative advantage in comparison to the trading partner.
Complementarity is of course a dynamic concept, and the complementary rela-
tionships between regions and countries can fade away, or may even be completely
reversed over the course of time. Nor is complementarity necessarily advanta-
geous to all countries or regions in the relationship—during the era of mercantil-
ism, regions that were held as colonial possessions by more economically
advanced countries, and which therefore had a high level of complementarity with
them, were exploited for their resources and denied the opportunity to develop
industries that might compete with those of the colonizing state. The decline of
the colonial era has not meant a diminution in complementarity, however. The
modern global economy is replete with examples of complementarity. Many
examples stem from the unequal distribution of crucial energy resources, vital
strategic metals, and the uneven nature of thegeography of economic develop-
mentthat has divided the world into “developed” and “underdeveloped” worlds
for the past three centuries. A high degree of complementarity exists between the
oil-producing countries of the Middle East, for example, and the industrialized
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