Geography Reference
In-Depth Information
MODEL OF THE DEMOGRAPHIC CYCLE
Stage 1
Stage 2
Stage 3
Stage 4
Stage 5
50
40
30
20
10
Figure 2.15
The Demographic Transition Model.
Five stages of the demographic transition.
© H. J. de Blij, P. O. Muller, and John Wiley & Sons, Inc.
0
Low growth
Increasing
growth
Population
explosion
Decreasing
growth
Declining
population
18th Century
19th Century
20th Century
21st Century
Future
WHY DOES POPULATION COMPOSITION
MATTER?
Maps showing the regional distribution and density
of populations tell us about the number of people in coun-
tries or regions, but they cannot reveal two other aspects
of those populations: the number of men and women and
their ages. These aspects of population, the
population
composition
, are important because a populous country
where half the population is very young has quite different
problems than a populous country where a large propor-
tion of the population is elderly. When geographers study
populations, therefore, they are concerned not only with
spatial distribution and growth rates but also with popula-
tion composition.
The composition is the structure of a population in
terms of age, sex, and other properties such as marital
status and education. Age and sex are key indicators of
population composition, and demographers and geogra-
phers use
population pyramids
to represent these traits
visually.
The population pyramid displays the percentages of
each age group in the total population (normally fi ve-year
increments) by a horizontal bar whose length represents
its share. Males in the group are to the left of the center
line, females to the right.
A population pyramid can instantly convey the
demographic situation in a country. In poorer coun-
tries, where birth and death rates generally remain
high, the pyramid looks like an evergreen tree, with
wide branches at the base and short ones near the top
10 billion in 200 years. The United Nations changed its
predictions based on lower fertility rates in many coun-
tries. All agencies reporting population predictions
have to revise their predictions periodically. In the late
1980s, for example, the World Bank predicted that the
United States would reach SPL in 2035 with 276 mil-
lion inhabitants. Brazil's population would stabilize at
353 million in 2070, Mexico's at 254 million in 2075,
and China's at 1.4 billion in 2090. India, destined to
become the world's most populous country, would
reach SPL at 1.6 billion in 2150.
Today these fi gures are unrealistic. China's popula-
tion passed the 1.2 billion mark in 1994, and India's
reached 1 billion in 1998. If we were to project an optimis-
tic decline in growth rates for both countries, China's
population would “stabilize” at 1.4 billion in 2025 and
India's at 1.7 billion in 2060, according to a 2011 United
Nations report. But population increase is a cyclical phe-
nomenon, and overall declines mask lags and spurts as
well as regional disparities.
Examine Appendix B at the end of the topic. Study the
growth rate column. Which countries have the highest
growth rates? Determine what stage of the demographic
transition these countries are in, and hypothesize what may
lead them to the next stage.
