Factors influencing population structures (Cambridge (CIE) IGCSE Geography) : Revision Note

Population pyramids

• The characteristics of a population—the distribution of age, sex, ethnicity, religion, etc.—are known as the population structure

• Information about these characteristics is gathered in a census

• The population structure is the result of changes in:

  • fertility

  • mortality

  • migration

• The two main components of age and sex can be shown on a population pyramid

What is a population pyramid?

• Population pyramids (also known as an age structure graph) are used to display the gender and age structure of a given population

  • They illustrate the distribution of the population across age groups and between male and female

• They enable governments nationally and regionally to assess the needs of the population for services such as healthcare and education

  • This means the governments can estimate and plan for spending

• As countries develop and pass through the stages of demographic transition, the shape of the population pyramid changes 

  • Each bar of the population pyramid represents a 5 year age range

  • The two sides of the population pyramid represent males (usually on the left) and females (usually on the right)

• The population pyramid can be used to identify the following groups:

  • Young dependants 

  • Old dependents 

  • Economically active (working population)

  • Dependency ratio 

Demographic transition and population structure

• As countries move through the stages of demographic transition

• The shape of the population pyramids reflect the changes

• LEDCs like Niger have a concave pyramid shape

• Stages 1 and 2 of the model and this indicates:

  • high birth rate

  • low life expectancy

  • high death rate but starting to decrease

  • high infant mortality rate

  • a young dependent population dominates

• LEDCs/NICs that are a little further along the demographic transition, such as Nepal, have a convex pyramid shape

• Stage 3 of the demographic transition model

• This indicates:

  • decreasing birth rate 

  • increasing life expectancy

  • decreasing death rate

  • decreasing infant mortality

  • larger working-age population

• MEDC countries such as the USA have a column-shape

• Stage 4 of the demographic transition model

• This indicates:

  • decreasing birth rate 

  • increasing life expectancy

  • decreasing death rate 

  • low infant mortality

  • larger working-age population

• MEDC countries such as Japan have a pentagon shape with a narrowing base

• Stage 5 of the demographic transition model

• This indicates:

  • Decreasing birth rate 

  • Increasing life expectancy

  • The death rate is higher than the birth rate due to the ageing population

  • Low infant mortality

  • Ageing population: older dependent population

Natural increase

• Natural increase is calculated by subtracting the death rate from the birth rate

• The combination of a decreasing death rate and high birth rate led to rapid natural increase and population explosion

• The impacts on population structure often leads to

  • a larger overall population

  • a population with a larger proportion of younger people

  • a higher dependency ratio

• A negative rate of natural increase happens when the birth rate is lower than the death rate

• When this occurs, it impacts the population structure, leading to:

  • a shrinking population

  • an ageing population

Net migration

• Net migration is calculated by subtracting the number of emigrants from the number of immigrants

  • The measurement is given per 1000 people

• Positive net migration occurs when there are more immigrants into a country than there are emigrants from the country

• Negative net migration occurs when there are more emigrants from a country than there are immigrants into the country

• In some countries, migration can lead to an imbalance in the population structure

• The UAE has significantly more males than females 

• Approximately 29% of the population are males between the ages of 25 and 39, whereas only 10.5% of the population are women between 25 and 39

  • This is the result of the migration of males to the UAE to work in the oil, gas and construction industries

• Rapid population growth in some areas as a result of migration can lead to:

  • increased pressure on services such as healthcare and schools

  • a shortage of housing

  • increased traffic congestion

  • increased water and air pollution

  • a shortage of food

  • a lack of clean water