First 228 words of the document:
Population structure is the number or % of males and females in different age groups within
a population. Population pyramids show population structure.
Here the base is very wide indicating a very high birth rate. The
width drops off very quickly. This means people must be dying.
Very few reach old age. Few countries are still in this stage
today but some rainforest populations would display this
Still a large base so high birth rate but also a wider and taller
pyramid as more people are living to older ages. This is stage
two of the demographic transition model and includes many
countries in Africa such as Kenya.
Note the more 'domed' shape. It means many people are living
to older ages as quality of life improves. There are also
proportionately fewer births. This is stage three of the
demographic transition model. Chile would be a good example.
Very small base due to the very low birth rates and death
rates displayed in the wide top.
This would be representative of Australia that has recently
come through stage three of the demographic transition
Birth rates drop below death rate and population declines.