Population Change

• There are two ways in which a population can change:

  • Migration 

  • Natural population change

Migration

• Migration can cause the population to either increase or decrease

• This occurs as the result of emigration or immigration

• Net migration is the difference between the number of people moving into a country (immigrants) and the number of people leaving the country (emigrants)

Exam Tip

Remember immigration and emigration are not the same. Immigration is the inward movement of people into a country. Emigration is the outward movement of people from a country.

Natural causes of population change

• There are many factors which have combined to cause the rapid population increase including improvements in:

  • Agriculture during the agricultural revolution led to higher yields and more varied diets

  • Medicine and medical care which reduces the death rate

  • Technology and transport, lead to a wealthier population which increases life expectancy

• All these factors led to a decrease in the death rate 

• The birth rate remained has remained high mainly in LEDCs due to:

  • Lack of access to family planning and contraception 

  • An increase in women surviving childbirth

  • Families continue to have large numbers of children to look after their parents in old age and to help support the family

  • The culture of having larger families which takes many years to change

  • Religious reasons 

• Natural change in population is calculated by deducting 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

• Population also changes as a result of migration into and out of a country/area

• Natural decrease occurs when the birth rate is lower than the death rate

Demographic Transition Model

• The demographic transition model illustrates the five generalised stages of population change that countries pass through as they develop

• It shows how birth and death rates change over time and how this affects the overall population as the country 

The Demographic Transition Model

Stage 1

• The total population is low 

• High birth rates due to lack of contraception/family planning 

• High death rates due to poor healthcare, poor diet and famine

• High infant mortality which leads people to have more children so that some children survive to adulthood

Stage 2

• The total population starts to rise rapidly

• Birth rates remain high as people continue to have large families

• Death rates decrease as a result of improved diets, better healthcare, lower infant mortality and increased access to clean water

Stage 3

• The total population continues to increase but the rate of growth begins to slow

• Birth rate begins to fall rapidly due to increased birth control, family planning, increased cost of raising children and low infant mortality rate 

• Death rate still decreasing but at a slower rate as improvements in medicine, hygiene, diet and water quality continue

Stage 4

• The total population is high and is increasing slowly 

• The birth rate is low and fluctuating due to accessible birth control and the choice of having fewer children as well as delaying the age women start to have children

• The death rate is low and fluctuates 

Stage 5

• The total population starts to slowly decline as the death rate exceeds the birth rate 

• The birth rate is low and slowly decreasing

• The death rate is low and fluctuates