The demographic transition model can be used to determine how the population pyramid looks like at all different stages. This gives a more visual presentation of population shape and changes.
Development: very low
Stage 1 is high and fluctuating, that is, both birth and death rate are fluctuating whilst still high. Small tribes often isolated from the world are in this stage. The resulting population pyramid is a broad base (high birth rate) and a dwindled top indicating a very low life expectancy.
Development: low e.g Zimbabwe, Tanzania, India
In this stage we begin to see a falling death rate, but birth rates still high. People will be more compliant to increase their life spans by following good health practice, thus lowering deaths. Conversely, birth rates are still high.
The population pyramid still has a broad base, but not much broad as in Stage1 and a relatively increasing top (high life expectancy).
Development: moderate, e.g China, Malaysia, Brazil
In this stage birth rates are rapidly reducing resulting in a more dwindled base. More people in the working class (youthful) giving a bulged middle section. Population growth is still increasing.
Birth rates continue to fall giving a more shrinked base. The mid section (working class) is more buldged. Deaths are low and Life expectancy high.
Country development: high
This stage was a prediction in the past, but some countries such as France are starting to go in this stage. Here, birth rates are intensely low while deaths are high (but still at low) such that the population does not replace itself thus greatly decreases. The pyramid is the vice-versa of Stage 1