Scientists use age structure to predict future growth patterns:
They analyze factors such as:
•Number and proportion of individuals in each age group.
•The number of males versus the number of females in each age group.
These numbers are used to construct age structure diagrams.
Scientists use age structure diagrams to:
1. Compare age groups such as pre-reproductive to reproductive ages
2. Compare the number of males to the number of females
The shape of the age structure diagram tells you:
1. If a population is increasing, stable or shrinking
2. Population growth momentum- even if people are having less children, the effect
won’t take place until much later when the children reach reproductive maturity.
Scientists use age structure diagrams to:
1. Compare age groups such as pre-reproductive to reproductive ages
2. Compare the number of males to the number of females
Scientists use the shape of the graph to determine:
1. If a population is growing, shrinking or staying the same
2. Growth momentum (how soon overpopulation will become a problem)
There are three scenarios:
1. Expanding/growing population- pyramid shape, has more children than any other age
group.- Nigeria or Bolivia
2. Stable populations- Number of children is roughly the same as the number of
reproductive adults- European countries
3. Declining population- Pre-reproductive group is smaller- Russia, Bulgaria and
Germany
Scientists use the shape of the graph to determine:
1. If a population is growing, shrinking or staying the same
2. Growth momentum (how soon overpopulation will become a problem)
3 possible shapes of an age structure diagram:
Shape:
Population Growth:
Pyramid
Rapid (more than 3
children per couple)
Block
Stable (2 children per couple)
Diamond
Shrinking (1 or less children
per couple)
Example:
Nigeria
U.S.
Germany