A country with a disproportionately large aging population has to deal with its ramifications. It can be a challenge when the generations following this group are significantly smaller. Their high numbers can be a burden on resources and the economy. The nature of their large numbers also means they have an influence on what policies are passed in a country.
There are several causes for one generation to exceed the numbers of those that follow it. One reason is a time period of a high amount of births per couple. This sometimes follows a traumatic national experience such as a prolonged war. The soldiers returning from the battlefield are motivated to start families and get life back to normal. This can influence couples to have a larger number of children.
A more controversial cause that changes a population is when governments mandate either more births or less. In the case of China there is a policy that strongly encourages parents to only have one child. There is only one person born in the country to end up supporting two people of an older generation. The younger generation is far smaller than that of their parents.
Trends in how many children are in each family can change from generation to generations. Decades ago people had many children to help out with the needs of their farms. There was also little access to birth control. Family planning is a far more accepted practice than it was just decades in the past.
More people are reaching older ages in many countries. This has occurred with the continued development of medical technology. There are pharmaceuticals and medical procedures that help increase expected lifespan. Many diseases that would have killed people in the past are no longer as deadly.
There is lobbying power in being the largest segment of a population. Politicians who are looking for votes will listen more intently to a larger group as opposed to a smaller one. Lobbying groups have been formed by the older population to lobby their democratic governments. They can have an influence on how government funds are spent. Politicians find programs for retired people easy to vote for since they represent a large voting block.
It is a common occurrence for current workers to be in a position to fund the programs for retired people. This is the type of system that is set up for monthly stipends as well as for medical care. There is a strain caused when the number of workers is far exceeded by the retired generation. An aging population can have an economic effect.