It can be used to show how the population growth of a country changes over a period of time.
it's very accurate
It's changed every month
It's useful for comparing populations between countries
Many people use it
What are the disadvantages ?
The model assumed that in time all countries would pass through the same stages however it has now become unlikely that Africa will go through the industrial stage ever.
It's not very accurate
The model assumed that the fall in death rate in stage 2 was the consequence of industrialisation. Initially the death rate in many British cities rose due to the insanitary conditions and only began to fall with the advances in medicine .
It's not good at predicting
In many counties the fall in birth rate in stage 3 countries has been less rapid than the model suggests due to religious and political opposition e.g one child policy.
Not enough people use it.
a population decline has been caused by several of the most economically developed countries falling below death rates e.g Germany so the model had to have a fifth stage added.
The time scale of the model is being squashed e.g Asia as they develop at much faster rates than in the industrialised countries