Population basics

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Demographic Transition Model (DTM)

The DTM shows how the population of a country changes over time through five stages. The model shows changes in birth rate, death rate and total population. 

Stage 1 - High fluctuating

Stage 2 - Early expanding

Stage 3 - Late expanding

Stage 4 - Low fluctuating

Stage 5 - Declining

As countries develop they move through the stages of DTM.

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DTM - Stage 1

High birth rate and high death rate

Birth rate and death rate fluctuate at a high level - the population remains stable but low. There aren't any countries in Stage 1, but some tribes in the rainforests of Brazil are in this stage.

  • Birth rate is high because there's no birth control or family planning, and education is poor.
  • It's also high because there's high infant mortality, so people have more children to replace those who've died.
  • Death rate is high and life expectancy is low because there's low because there's low health care, sanitation and diet - leading to disease and starvation.
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DTM - Stage 2

Death rate falls, but birth rate remains high - the population increases rapidly.

Countries like Nepal and Afghanistan are still in Stage 2.

  • Birth rate is high as there's still little birth control or family planning and education is poor.
  • Birth rate also stays high for labour reasons - family members all have to work. A larger family can tend to a larger farm, helping to bring in more food and money.
  • Death rate falls and life expectancy increases due to improved health care, sanitation and diet.
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DTM - Stage 3

Birth rate declines rapidly, while death rate falls slowly - the population increases at a slower rate. Countries like Egypt are in Stage 3.

  • Birth rate decreases due to the increased use of birth control and family planning. 
  • The birth rate also drops as the economy moves towards manufacturing - fewer children are needed to work on farms, so having a larger family isn't as food as it once was.
  • Birth rate falls further still as women work rather that stay at home to have children.
  • Some countries introduce government population policies to try to reduce the birth rate.
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DTM - Stage 4

Birth rate and death rate fluctuate at a low level - the population remains stable but high. Most developed countries, e.g. most of Europe and the USA, are in Stage 4.

Birth rate remains low because access and demand for luxuries like holidays and material possessions means that there's less money available for having children.

Also theres fewer advantages to having children.

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DTM - Stage 5

Birth rate begins to decline further while death rate remains stable - the population begins to decrease. Some highly developed countries, e.g. Japan, are in Stage 5. 

  • The birth rate decreases because children are expensive to raise and many people have dependent elderly relatives, so lots of people choose not to have children.
  • Death rate remains steady as there are more elderly people so more people die despite advantages in health care.
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Population structure

Population structure is the number or % of males and females in different age groups within a population.

Population pyramids (age-sex pyramids) show population structure. 

You can learn a lot about the demographics of a place from its population pyramid.

Population pyramids for different countries vary because of differnet demographic factors - birth rates, death factors, fertility rates, wars, migration etc.

A country's population structure changes through time as it moves through the DTM.

This means that a population pyramid can show which stage of the DTM a country is in.

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Migration changing population structure

Migration can affectany part of the population pyramid - it depends on the age of the migrants are.

Internal migration

Internal migration from rural areas to urban areas often affects the number of young adults. They move away from the countryside into cities to get a job. This is rural-urban migration. This can affect birth rate too as the migrants are of reproductive age.

Emigration away from countries at later DTM stages

Decreases the population of the country they've left, e.g. elderly people in the UK retiring to other countries - reduces the grey population in the UK but increases the grey population in the countries they move to.

Immigration into countries at later DTM stages

Increases the population of people of working and reproductive age. This increases the population of young people and increases birth rate, e.g. immigration into the UK (Stage 4).

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