Analysing Population Pyramids

The demographic transition model

The demographic transition model shows population change over time. It studies how birth rate and death rate affect the total population of a country.

The five stages of the demographic transition model:

  1. Total population is low but it is balanced due to high birth rates and high death rates.
  2. Total population rises as death rates fall due to improvements in health care and sanitation. Birth rates remain high.
  3. Total population is still rising rapidly. The gap between birth and death rates narrows due to the availability of contraception and fewer children being needed to work – due to the mechanisation of farming. The natural increase is high.
  4. Total population is high, but it is balanced by a low birth rate and a low death rate. Birth control is widely available and there is a desire for smaller families.
  5. Total population is high but going into decline due to an ageing population. There is a continued desire for smaller families, with people opting to have children later in life.

demographic_transition_detailed

As a country passes through the demographic transition model, the total population rises. Most LEDCs are at stage 2 or 3 (with a growing population and a high natural increase). Most MEDCs are now at stage 4 of the model and some such as Germany have entered stage 5.

The demographic transition model

As populations move through the stages of the model, the gap between birth rate and death rate first widens, then narrows. In stage 1 the two rates are balanced. In stage 2 they diverge, as the death rate falls relative to the birth rate. In stage 3 they converge again, as the birth rate falls relative to the death rate. Finally, in stage 4 the death and birth rates are balanced again but at a much lower level.

Limitations of the model

  1. The model was developed after studying the experiences of countries in Western Europe and North America. Conditions might be different for LEDCs in different parts of the world.
  2. The original model doesn’t take into account the fact that some countries now have a declining population and a 5th stage. Most texts will now show this stage as it is relevant to an increasing number of MEDCs in the 21st century.

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.

Population pyramid for the UK 2000/2016

Resultado de imagen de population pyramid 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.
  • A narrow base that shows a low birth, so not very young
  • A broad shape at the top that shows a high proportion of people living longer. Women live longer than men.
  • The bulge in the middle of the pyramid showing a baby boom /high rate of births) related to a proper period, no wars, growth, etc., over 1960´s and 1970´s.
  • And compare to 2016 pyramid there is a bulge in the area 45 -54 (16 years later than the bulge in 2000 UK´s pyramid). Births have decreased lightly, and life expectancy have increased. There are more ageing people.

Population pyramid for Mozambique 2000/2016

Resultado de imagen de population pyramid 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.
  • A narrow shape on the top shows a low proportion of people living in old-age and a high death rate. Women live longer than men. Low life expectancy.
  • The middle shapes show many young dependants. In 15-19 aged-group there is an indent high mortal rate than normal related to war, famine, disease, emigration, etc.
  • A wider shape on the base shows a high birth rate and a large number of children. Fewer baby girls than baby boys, but boys had a high infant mortal rate than girls.
  • 2016 pyramid show us very similar data. Not many differences in Births, nor in deaths.

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.

Population numbers change over time, influenced by births, deaths and migration into or out of the area. Global population levels, having grown slowly for most of human history, are now rising.

Typical pyramids

MEDC/LEDC Occupational Structures
Primary Secondary Tertiary
MEDC Very low. Machines have largely replaced human labour on the farms. Low. Automation is increasingly replacing human labour in factories. Globalisation is leading to a shift of manufacturing jobs to the NICs. High. Large numbers are employed in education, health, administration and the knowledge economy
LEDC Large primary sector (farming). Exports are usually primary commodities. Low. Tariff barriers imposed by the trading blocs such as the EU prevent the export of cheap manufactured products. The domestic market is very small. Large service sector. Many employed in the informal economy.
NIC Shrinking primary (farming) sector. Secondary sector is large and growing (transnationals). Small but growing tertiary sector to serve the needs of the transnationals

http://www.bbc.co.uk/schools/gcsebitesize/geography/population/population_change_structure_rev1.shtml

http://geographyfieldwork.com/PopulationStructure.htm

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