BBC- GCSE Population
Population Change and Structure
Population numbers change over time, influenced by births, deaths and
migration into or out of the area. Global population levels, having grown slowly
for most of human history, are now rising.
Global population growth
Population pyramids show the structure of a population by comparing relative
numbers of people in different age groups. Population structures differ markedly
between LEDCs and MEDCs.
Demographic transition models show population change over time - and also show
marked differences between LEDCs and MEDCs.
At present the world's population is growing quickly, though this has not always been the
case.
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Until the 1800s the world's population grew slowly for thousands of years.
In 1820 the world's population reached one billion.
In the early 1970s, the world's population reached three billion.
In 1999, less than 30 years later, the population doubled to six billion.
The global rate of population growth is now one billion every 15 years.
The graph shows this pattern of accelerating growth (including the predicted population
for 2025).
World population growth 500BC - 2025
Causes and rates of change
The three main causes of population change
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Births - usually measured using the birth rate (number of live births per 1,000 of the
population per year).
Deaths - usually measured using the death rate (number of deaths per 1,000 of the
population per year).
Migration - the movement of people in and out of an area.
Rate of change
Births and deaths are natural causes of population change. The difference between the
birth rate and the death rate of a country or place is called thenatural increase. The
natural increase is calculated by subtracting the death rate from the birth rate.
natural increase = birth rate - death rate
The rate of natural increase is given as a percentage, calculated by dividing the natural
increase by 10. For example, if the birth rate is 14 per 1,000 population, and the death
rate is 8 per 1000 population, then the natural increase = 14 - 8 = 6. That is 6/1000, which
is equal to 0.6 per cent.
Causes and rates of change
The three main causes of population change
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Births - usually measured using the birth rate (number of live births per 1,000 of the
population per year).
Deaths - usually measured using the death rate (number of deaths per 1,000 of the
population per year).
Migration - the movement of people in and out of an area.
Rate of change
Births and deaths are natural causes of population change. The difference between the
birth rate and the death rate of a country or place is called thenatural increase. The
natural increase is calculated by subtracting the death rate from the birth rate.
natural increase = birth rate - death rate
The rate of natural increase is given as a percentage, calculated by dividing the natural
increase by 10. For example, if the birth rate is 14 per 1,000 population, and the death
rate is 8 per 1000 population, then the natural increase = 14 - 8 = 6. That is 6/1000, which
is equal to 0.6 per cent.
Patterns of population growth
Rates of population growth vary across the world. Although the world's total population
is rising rapidly, not all countries are experiencing this growth. In the UK, for example,
population growth is slowing, while in Germany the population has started to
decline. MEDCs have low population growth rates, with low death rates and low birth
rates.
Population will decline if death rate is greater than birth rate.
Population will increase if death rate is less than birth rate.
LEDCs have high population growth rates. Both birth rates and death rates in LEDCs
tend to be high. However, improving healthcare leads to death rates falling - while birth
rates remain high.
The table shows data in selected LEDC and MEDC countries. The figures are per 1,000 of
the population per year.
MEDCs
Country Birth rate Death rate
Natural increase
Population growth rate (%)
UK
11
10
1
0.1
Canada
11
7
4
0.4
Bulgaria
9
14
-5
-0.5
LEDCs
Country
Birth
rate
Death
rate
Natural
increase
Population growth rate
(%)
South
Africa
25
15
10
1
Botswana
31
22
9
0.9
Zimbabwe
29
20
9
0.9
In Bulgaria, the birth rate is 9/1,000 and death rate is
death rate, Bulgaria has a declining population.
/1,000. As birth rate is less than the
14
In South Africa, the birth rate is 25/1,000 and death rate is 15/1,000. South Africa has
an increasing population with a population growth rate of 1 per cent.
The demographic transition model
The demographic transition model shows population change over time. It studies how
birth rate and death rate affect the total population of a country.
The five stages of the demographic transition model
1. Total population is low but it is balanced due to high birth rates and high death
rates.
2. Total population rises as death rates fall due to improvements in health care and
sanitation. Birth rates remain high.
3. Total population is still rising rapidly. The gap between birth and death rates narrows
due to the availability of contraception and fewer children being needed to work due to the mechanisation of farming. The natural increase is high.
4. Total population is high, but it is balanced by a low birth rate and a low death rate.
Birth control is widely available and there is a desire for smaller families.
5. Total population is high but going into decline due to an ageing population. There is
a continued desire for smaller families, with people opting to have children later in
life.
As a country passes through the demographic transition model, the total population
rises. Most LEDCs are at stage 2 or 3 (with a growing population and a high natural
increase). Most MEDCs are now at stage 4 of the model and some such as Germany
have entered stage 5.
The demographic transition model
As populations move through the stages of the model, the gap between birth rate and
death rate first widens, then narrows. In stage 1 the two rates are balanced. In stage 2
they diverge, as the death rate falls relative to the birth rate. In stage 3
they converge again, as the birth rate falls relative to the death rate. Finally in stage 4
the death and birth rates are balanced again but at a much lower level.
Limitations of the model
1. The model was developed after studying the experiences of countries in Western
Europe and North America. Conditions might be different for LEDCs in different parts
of the world.
2. The original model doesn't take into account the fact that some countries now have
a declining population and a 5th stage. Most texts will now show this stage as it is
relevant to an increasing number of MEDCs in the 21st century.
Population structure and population pyramids
Population structure means the 'make up' or composition of a population. Looking at the
population structure of a place shows how the population is divided up between males
and females of different age groups.
Population structure is usually shown using a population pyramid. A population
pyramid can be drawn up for any area, from a whole continent or country to an
individual town, city or village.
The following graphs show the population pyramids of an MEDC (the UK) and an LEDC
(Mozambique), for 2000 and in 2025 using projected figures. The left side of each
pyramid shows the number of men in each age group, the right side shows the number
of women in each age group.
Population pyramid for the UK 2000
Notice how in the UK 2000 pyramid there is a bulge in the area of the 30-34 and 35-39
age groups, with the numbers thereafter reducing fairly steadily as the ages increase.
This matches stage 4 of the demographic transition model.
Projected population pyramid for the UK 2025
Compare this to the 2025 pyramid, which would be stage 5 in the model. Here the bulge
extends much further, covering the age groups 30-64, with the numbers beginning to
reduce significantly only after 64.
Now compare the UK population pyramids with those for Mozambique:
Population pyramid for Mozambique 2000
In this graph, notice that in 2000 the 0-4 age group contained the largest number of
people, with the numbers thereafter declining steadily as the ages increase. The graph
matches stage 1 in the model.
Projected population pyramid for Mozambique 2025
In the second graph, the largest group in Mozambique in 2025 is still the 0-4 age group,
but there are nearly as many people in the 5-29 age groups. Now the population
pyramid matches stage 2.
Analysing population pyramids
Key things to know about population pyramids
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The shape of a population pyramid can tell us a lot about an area's population.
It gives us information about birth and death rates as well as life expectancy.
A population pyramid tells us how many dependants there are. There are two groups of
dependants; young dependants (aged below 15) and elderly dependants (aged over 65).
Dependants rely upon the economically active for economic support.
Many LEDCs have a high number of young dependants, whilst many MEDCs have a
growing number of elderly dependants.
How do pyramids change over time?
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A population pyramid that is very triangular (eg Mozambique in 2000) shows a
population with a high number of young dependants and a low life expectancy.
A population pyramid that has fairly straight sides (more like a barrel) shows a
population with a falling birth rate and a rising life expectancy.
Over time, as a country develops, the shape changes from triangular to barrel-like.
Places with an ageing population and a very low birth rate would have a structure that
looks like an upside-down pyramid.
Population change and structure - Test
1.
The three main factors that cause population change to a specified area are:
births, deaths and marriage.
births, deaths and migration.
births, deaths and life expectancy.
2.
The natural increase of a population is the difference between the country's birth rate
and what?
Migration rate
Marriage rate
Death rate
3.
How is the world's population changing?
Rapidly increasing
Slowly increasing
Slowly decreasing
4.
When did the world's population start to grow more rapidly?
1700s
1800s
1900s
5.
In 2025, there could be how many people on the planet?
8.5 billion
12 billion
18 billion
6.
Does the rate of population growth tend to be higher in MEDCs or LEDCs?
MEDCs
LEDCs
7.
What does population structure refer to?
The different types of buildings that people live in.
How the population of a region or country get along with one another.
The composition of the population of an area.
8.
What is a population pyramid?
A graphical representation of the population structure of an area
When the population density of a location is so high that people have to live in high
rise properties
The pattern of population distribution in large urban areas
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