lack of balance between birth and death rates is particularly
pronounced in many developing countries experiencing population
momentum. This phenomenon occurs when a large proportion
of a countrys population is of childbearing age. Even
if the fertility
rate of people in developing countries reaches replacement
level, that is if couples have only enough children to replace
themselves when they die, for several decades the absolute
numbers of people being born still will exceed the numbers
of people dying.
3.1 and 3.2
3.1 and 3.2 show the composition of the population by
age and gender in 2000 and 2030 for low- and high-income
economies. As can be seen in Chart 3.1, there is a large
difference in low-income countries between the percentage
of people of childbearing age and more elderly adults. Once
this young group moves beyond childbearing age, however,
the momentum will decrease, and population can begin to
stabilize so that births and deaths balance (assuming fertility
rates remain at or below replacement levels). The reverse
is true in many high-income countries where birth rates
have already been low for several decades and populations
have either stabilized or in some cases begun to decline.
does the age of its population affect a country?
countries more than a third of the population is under age
15, compared with less than a fifth in high-income countries.
This means that a larger portion of the low-income countries
population is too young to work and, in the short run, is
dependent upon those who can.
the transition to lower population growth rates can pose
problems, too. As growth slows, the average age of the population
rises and eventually the proportion of elderly, nonworking
people will increase. This puts great pressure on the working-age
population and on a countrys pension, health care,
and social security systems. This is an issue facing some
high-income countries today and one that may face developing
countries in the future as their population growth rates
continue to decline.
migration has important social, economic and political significance.
This is as true for countries that lose citizens to immigration
as it is for the countries in which immigrants make their
new homes. Although attention is often given to the numbers
of people migrating from developing to industrial countries,
most migration in the world today occurs between developing
is also significant. The rapid growth of cities in developing
countries is nearly universal. Whereas less than 22 percent
of the developing worlds population was urban in 1960,
by 1990 it had increased to 34 percent. By 2015 it is expected
to reach 48 percent.
movement of people from rural to urban areas can result
in greater production of goods and services, but it can
also create congestion, pollution, and a greater demand
for housing, clean water, sanitation facilities, recreation
areas, public transport, health care and education. When
rapid migration to cities strains the capacities of governments
to provide these necessary services, the result may be a
lower standard of living for everyone.