Perspectives
on the Problem of World Population Growth |
The
Malthusian Dilemma. The most famous and perhaps most influential model
of world population growth was proposed by Thomas Malthus, an English clergyman,
over two centuries ago. Malthus argued that human populations grow geometrically
or exponentially--that is, by doubling every few generations, as
in the series 2-4-8-16. In contrast, he contended that food resources could
only increase arithmetically or in additive increments, such
as 4-5-6-7. As shown in the following diagram, Malthus believed that, at
these differing rates of growth, a population would eventually outstrip
its supply of food. At that point, positive checks on population
growth--famine, disease, and war--would come into play and bring
the population back into balance with its food resources. |
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The
Population Growth Equation.
The field of demography deals with the growth and composition of
human populations. Demographers basically deal with three variables that
affect population change: (B) the fertility
or birth rate; (D) the mortality
or death rate; and (M) the net
migration rate. As depicted in the following equation, which is typically
referred to as the population growth (or balancing) equation, the
rate of change (delta) in a given
population (P), is a function of these
three variables. |
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The
Demographic Transition Model.
Kingsley Davis, a well-known demographer, formulated a relatively simple
model that describes different historical stages in the growth of populations.
Davis originally applied this model to changes that occurred in Western
European populations over the course of several centuries, beginning with
the pre-industrial Middle Ages and ending with the industrialized 20th Century.
However, the model is also useful for describing the current problem of
rapid population growth in developing nations, which have experienced a
dramatic decline in death rates while birth rates have remained relatively
high. As shown in Stage 2 below, the shape decline in death rates in developing
nations after World War II has resulted in a high rate of natural increase
in their populations. Some nations in Asia and Latin America appear to be
entering Stage 3, but the gap between birth rates and death rates remains
large in many regions of the Third World. |
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Population
Pyramids. |
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Index Page
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