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
Projected population pyramid for the UK 2025
Now compare the UK population pyramids with those for Mozambique:
Population pyramid for Mozambique 2000
Projected population pyramid for Mozambique 2025
Causes and rates of change
The three main causes of population change
- 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 the natural 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 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.
Population pyramids: Are a way of displaying the age / sex structure of a population. We can analyse it to predict the future and plan accordingly.
Dependency ratios: This is a ratio that compares the percentage of population available for work (15-64) and those economically inactive.
You can work it out: (All children 14 and under plus those aged 65 and over) divided by (number of adults aged 15-64).
The higher the ratio the more potential problems for the future.
Population structures: This is the age/sex balance that exists.
This is very closely linked to the demographic transition model and migration. You could be asked to talk about the population structure of an area and the implications of that structure for the future. In English, what is the percentage of males and females, how old are they and why does it matter.
The usual way to show this is with a population pyramid. This is simply a combination bar graph showing the percentage of males at different ages and the percentage of females at different ages. It can however tell us a lot about a country and its development.
Pyramid 1: Here the base is very wide indicating a very high birth rate. The width drops off very quickly. This means people must be dying. Very few reach old age. Few countries are still in this stage today but some rainforest populations would display this pattern.
Implications: Clear need for investment into water supplies, health care, food supplies and housing to reduce death rates.
Pyramid 2: Still a large base so high birth rate but also a wider and taller pyramid as more people are living to older ages. This is stage two of the demographic transition model and includes many countries in Africa such as Kenya.
Implication: Probable need to invest in education about family planning to reduce birth rate. Possibly indicates that women are undervalued in society so this could be tackled.
Pyramid 3: Note the more 'domed' shape. It means many people are living to older ages as quality of life improves. There are also proportionately fewer births. This is stage three of the demographic transition model. Chile would be a good example.
Implication: As the population becomes increasingly older there may be a need to invest in facilities and services for them. Still a need for continued investment in family planning.
Pyramid 4: Very small base due to the very low birth rates and death rates displayed in the wide top. This would be representative of Australia that has recently come through stage three of the demographic transition model.
Implication: Should the situation continue there are serious implications about providing for the elderly population (increasing cost of health care, state pensions) especially as the working population becomes proportionally smaller. This is a major concern in much of the developed world.
Population pyramids can also be influenced by:
Migration: Likelihood of extra young males as these are likely to migrate.
Famines: Clear drops in population especially among the very young as these are most likely to suffer.
War: Clear drop off in male populations of fighting age.
Make sure you can read data from a pyramid - try the one in the questions section
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