POPULATION PYRAMIDS

This is an interesting way to see how the Spanish Population is changing...

Aprende más sobre las Pirámides de Población (español)

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

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

• 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?

• 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.