The term population structure refers to the composition of a population. The
population structure of a country is usually shown using a population pyramid.
A population pyramid is a graphical representation that shows the
distribution of various age groups and gender in a population. The male
population is represented on the left hand side of the pyramid and the females
on the right. Age groups are arranged in five-year intervals beginning with 0 to
4 years old, followed by 5 to 9 and so on. Population pyramids can also be used to
show the population structure for cities and towns. Population structures differ
markedly between less economically developed countries and more
economically developed countries. The demographic information we see on
pyramids is collected by governments during a census. This information helps
them to assess the present and future needs of a country. For example, what is
the likely tax take going to be. How much will have to be budgeted for health
care and education. How much money needs to be set aside for pensions. There are
three main population pyramid shapes. Less economically developed countries
typically have a youthful growing population. The country represented on
this pyramid has a high birthrate which is shown by the broad base on the
pyramid. Each consecutive age group moving up the pyramid gets narrower due
to the high death rates and a short life expectancy. This youthful population is
characterized by large families, many children and few old people. Population
growth is rapid. Uganda is an example of a country in this category with 49.9%
being under 14 years old and only 2.1 living beyond 65 in 2012. Civil war,
diseases such as aids and poverty have contributed to the high death rates. A
youthful population has a high dependency ratio. This is the ratio of
the working age population to those who are dependents. That is the young
dependents below 15 and the elderly dependents aged over 65 who are retired.
The working age population from 15 to 65 has to provide for a comparatively large
population of children. Countries with population pyramids like this resemble
countries in the first stage of demographic transition. As the population
ages a more beehive like structure develops, as can be seen in this example
of the UK pyramid below. This country has a declining birthrate and a lower death
rate with more people living longer. This structure is called an aging population.
Many more economically developed countries in the fourth stage of
demographic transition have a population structure like this. This is likely due
to factors such as a more widespread use of contraception, delayed marriage, and
better health care. Notice how in this pyramid for the United Kingdom there's a
bulge in the area of the middle age groups. This is related to the larger number of
people born in the United Kingdom from 1946 to 1971, with the peak coming around
1947. We call this generation the baby boomers because of the baby boom that
followed the Second World War. As this population ages the bulge of the baby
boomers will climb up the pyramid. Also notice that in the older age groups
there's no symmetry between males and females. This is due to the tendency for
females to live longer on average than males. This aging population has
implications for governments that will have to meet future medical needs and
aged services. The Australian government for example responded to projections and
the numbers of old people by raising the retirement age from 65 to 67. The third
type of population pyramid shows an aged population.
This type of pyramid is typical of a country in the fifth stage of
demographic transition such as this pyramid below. Here the Bulge is found
higher up the pyramid, with the numbers beginning to reduce significantly only
after 64. They have low birthrates, fewer children and low death rates. Thus
the population starts to shrink. They also have a high dependency ratio. That
is, there are fewer working age people to support the growing numbers of older
people. There are also more healthy old people as life expectancies are longer
due to modern health care and better living conditions. Life expectancy is a
measure of how long a person can expect to live from birth. Japan for example has
one of the highest life expectancies in the world at 84.6
but also has a shrinking population. From 2010 to 2014 Japan's population shrank
by 0.7 percent going from 128.6 million
to 127.2 million. Japan's population is
projected to have over 40 percent aged over 65 by the Year 2060. Like Japan,
countries showing this population structure tend to be wealthy and highly
urbanized.