Population
Pyramids
We are
working
through pages
175 to 178
An Introduction to Population Pyramids
• The composition of any population, that is, the ages and sex of the
members of that population, is of particular interest to
demographers.
• Typically demographers categorize any population into its male and
female components by age divisions called cohorts. The most
common cohorts are divided into 5 year intervals.
• This information can be presented using an age-sex structure
called a population pyramid, as the information pertaining to
countries resemble a triangular or pyramidal shape.
• In a population pyramid, bars indicating the male portion of the
population extend to the left of a vertical axis, while bars indicating
the female portion extend to the right.
• The bars are stacked on top of each other, starting with the bars for
the youngest cohort at the bottom.
1996 Census of
Population
• In modern times a population pyramid tends to be classified as
either expansive or stationary.
• Expansive Age-sex Structure: A population pyramid with a
wide base and narrower top. This indicates a high birth rate and
an expanding population.
• Population pyramids of LDCs (Less Developed Countries) typically
have a wide base and a narrow top. This represents a high birth rate
and high death rate.
• Stationary Age-sex Structure: A population pyramid that
indicates no or very little population growth. Stationary age-sex
structures are characteristic of countries where both the death
rate and birth rate are very low. The pyramid is characterized by
relatively straight sides.
• Population pyramids of MDCs (More Developed Countries) typically
have a roughly equal distribution of population throughout the age
groups. The top obviously gets narrower as a result of deaths.
Different Ages – Different Roles
•
At each stage of our lives, we play different roles. Demographers identify three
important stages:
• Children (up to age 15)
• Working adults (ages 16 to 64)
• Other adults (65 and over)
•
The assumption is that children and older adults are not working and must be
supported by the working population.
•
The proportion of the population that must be supported is called the dependency
ratio. We can calculate the dependency ratio by adding together the percentage of
those under fifteen and those over sixty-four, and then dividing this sum by the
percentage of those in the potential labour force (ages 15 to 64).
•
For example, (see page 175 in the text) using the population pyramid of Canada in
1961, the dependency ratio for each member of the potential work force, plus himself
or herself, supports 0.73% or you could say that there are 73 dependants for every
100 people in the potential labour force.
Percent under 15 + percent over 64 = 33.8 + 8.4
Percent 15-64
57.8
=
0.73%
• A high dependency load, of either children or
older people, tends to put a great deal of
pressure on the society to provide education,
housing, health care, old-age homes, and other
needs.
• Canada today has a dependency load of 33%
(21% children and 12% older people), while a
country like Niger in north Africa has a
dependency load of 52% (49% children and only
3% older people).
• You can imagine the difficulty that a country like
Niger would have in trying to support the more
than half of its population that is dependent.
Turn to page 177
• Refer to Q. 27 (a) – Begin this question by constructing a population
pyramid for Japan. Refer to Figure 7.28 for your data information.
Use landscape form. Label the population pyramid at the top of the
page – Japan (1997).
• Next, Count over 28 squares and draw a line from the top of the
graph to the bottom. Draw a line from the bottom of line 32
upwards. Between these two established lines are your age groups.
Every two rows equals an age group, starting at 0-4 and finishing
the pyramid at 80+).
• On the left-side of the pyramid is your male percentages, and on the
right-side of the population is your female percentages. On either
side of the age group bar in the middle, each line going over is .25
percent. Start at zero (age group lines).
• Materials: (1) Use the graph paper that has been provided. (2) You
will require two colour pencils. Use one colour to shade in the bars
for male percentages on your pyramid. Choose an additional colour
to shade in the bars representing the female percentages.
Age-sex Distribution for Japan (1997)
% Male
Age Group
%Female
2.4
0-4
2.3
2.5
5-9
2.4
2,9
10-14
2.8
3.3
15-19
3.1
3.9
20-24
3.7
3.9
25-29
3.7
3.3
30-34
3.2
3.1
35-39
3.1
3.3
40-44
3.3
4.3
45-49
4.3
3.4
50-54
3.5
3.2
55-59
3.3
2.9
60-64
3.1
2.5
65-69
2.8
1.8
70-74
2.3
1.0
75-79
1.7
1.1
80+
2.2
Turn to page 178
• Once you constructed the pyramid for
Japan, using the data in Figure 7.28 on
page 178, construct a population
pyramid for Malawi. Follow the steps
used in the instructions for constructing
the population pyramid fro Japan. In
counting over from the age groups,
count each block as.5% instead of .25%.
• Once completed, answer Q.
27 (PARTS B, C, D, and E)
for the population pyramids
for Japan and Malawi.
Age-sex Distribution for Malawi (1997)
% Male
Age Group
%Female
8.5
0-4
8.4
7.6
5-9
7.6
6.9
10-14
6.8
5.9
15-19
5.8
4.9
20-24
4.7
3.9
25-29
3.7
2.8
30-34
2.8
2.1
35-39
2.2
1.6
40-44
1.9
1.4
45-49
1.7
1.1
50-54
1.4
0.9
55-59
1.2
0.7
60-64
0.9
0.5
65-69
0.7
0.3
70-74
0.5
0.2
75-79
0.2
0.1
80+
0.1
Demographic Transition
Models
The Demographic Transition Model
• The Demographic Transition Model attempts to show how
population changes as a country develops. The model is divided into
four stages.
• Stage 1
Birth rate and death rate are high - low natural increase - low total
population
• Stage 2
Birth rate is high - death rate is falling - high natural increase
(population growth)
• Stage 3
Falling birth rate - low death rate - high natural increase (population
growth)
• Stage 4
Birth rate and death rate is low - low natural increase - high total
population
Population Changes in LDCs
• The populations of less developed countries (LDCs) are growing
very rapidly. Most are at stage 2 and 3 of the Demographic
Transition Model. They have declining deaths rates and high birth
rates. Therefore, natural increase is high.
• Death rates are declining because of
improvements in sanitation and healthcare.
• Birth rates are high for a number of reasons:
• Lack of family planning education or contraceptives
• In rural areas children are needed as labour on farms. In urban
areas they are needed to work in the informal sector to earn money
for their families.
• Women have a large number of children as there is a high level of
infant mortality
• Culture/religion mean it is unacceptable to use contraceptives
Population Changes in MDCs
• In most MDCs population growth is stable. MDCs have
low birth and death rates. In some countries (i.e.
Germany) the birth rate is actually lower than the death
rate. This means there is a decrease in population
versus a natural increase (Germany is -0.1%).
• The major problem for many MDCs is an ageing
population.
• Life expectancy in MDCs is increasing as people are
now living longer due to improvements in health care,
diet and lifestyle.
• Therefore, there will be a a greater number of elderly
dependents. In the UK this is likely to lead to increased
taxes to pay for health care and pensions.
Sources
• http://www.census.gov/ipc/www/idbpyr.html
• http://www.geography.learnontheinternet.co.uk/