When Heidi shows the dependency ratio best
What is a Dependency Ratio?
Human beings all rely on others at various points in their lives, especially during childhood and elder years. "Depency Ratio" is a term coined to represent how many children (usually under 14) and elderly people (65+) there are in comparison to the independent adult population. Since children and elderly people are either not able to work, or not able to work at the rate they need, they depend on other people and the government for help. The dependency ratio helps us determine if we have a safe balance.
Therefore it is up to the independent people to provide support, through taxes, to help pay for the monetary, educational, and health benefits the dependents need. The more dependent people there are, the bigger the dependency ratio, the greater the strain to provide funds to support the population.
Books about Population Growth: A factor for Dependency Ratios
What causes the dependency ratio to change?
People living longer
Better medecine does usually correlate people living longer. However, the medicine still can't keep up with the fact that they've aged and therefore probably no longer can work.
Too many children being born
WWII deeply affected the dependency ratio because, when the war ended, so many people were having children. Even though those child eventually grew to be adults, thus lowering their effect on the dependency ratio, many of them ended up having children of their own. Consequences can happen.
Not enough children being born
Likewise, if not enough children are born, the dependency ratio will temporarily go down, but then it'll go back up as there are more new elderly people than new adults.
Bad living conditions
If living conditions in a country are unsatisfactory, people may leave. This would cause an unpredictable change in the dependency ratio (good or bad).