First 113 words of the document:
Using Population Pyramids for predictions.
A population pyramid represents a snapshot of a country's population at any one
time. However, a pyramid can be animated to show how that country's population
might develop in future.
· The present population structure.
· Present birth rates and fertility rates.
· Present death rates and life expectancy.
· Predictable future variations in the vital rates.
These variables are used to predict how many children will be born to each group of
the pyramid as they move through the age ranges, and then how long the members of
each group will survive.2000