Population Aging: How a Population's Age Structure Changes

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  • 0:01 Aging Population
  • 1:45 Mechanisms of Change
  • 4:51 Dependency Ratio
  • 6:42 Lesson Summary
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Lesson Transcript
Instructor: Devin Kowalczyk

Devin has taught psychology and has a master's degree in clinical forensic psychology. He is working on his PhD.

This lesson explores what it means for a population to start aging. In addition, we'll also explore the primary mechanisms of what ages a population and how this influences the ratio of workers to non-workers.

Aging Population

When writing a lesson, I am handed a set of instructions and things to cover. Sometimes they are super straightforward and really logical, like for a video about a neuron where it tells me the main parts of the neuron the bosses want me to cover. But sometimes I am given an instruction that I have to read and re-read.

Today's lesson had one line that was 'Explain why a population ages.' And I just stared at it and thought 'Because people get older.' But, of course, this was not the answer that was appropriate. In this lesson, we are going to go more in-depth and look at why a population is seen as graying, which is when the percentage of the population over the age of 65 increases.

This term, graying, is quite popular with the media because it comes with a certain connotation. It is usually linked to all of the social services, like Medicaid and social security, and the increased demand for services. But graying is just a colorful term used to describe how populations can transition from a youth-based culture to one with more elderly people in it.

In this lesson, we will look at the mechanisms of why the ratio of older people to younger people will change. They can be concisely described as babies being born (or fertility), people dying (or mortality), and people moving (or migration). Furthermore, these changes to a population can also be represented by a dependency ratio, which looks at workers to non-workers.

Mechanisms of Change

When we talk about mechanisms for changing a population, of shifting it from youthful to more elderly, we can get caught up too much in the nitty-gritty. I already told you that we would cover the three main mechanisms, that being fertility, mortality, and migration. The reason these are the main three is that most other aspects that change a population are subsumed into these. Birth control lowers a population? Fertility. War breaks out? Mortality. People don't like the food? Migration. Now that you have a basic idea of why we are covering these, let's look at them more specifically.

Fertility, or the rate of childbirth, can tilt the scales. I like that metaphor, so let's use it. Let's imagine a three tabled scale, with children, middle aged, and older people on each scale. If fertility drops, like it has in China, with the one child policy, or in Japan, where there are fewer resources and the cost of raising a kid is extremely high, then the scale will begin to tilt towards middle aged and then eventually older people. There are not as many young people to balance it out. This will likely eventually cause the population to shrink because there aren't as many people having babies!

Mortality, or the rate of death, can also tilt the scales. If, for instance, a large and bloody war were to happen and all of the middle aged people were drafted for the war, then this would mean that children and old people would make up a larger percentage of the population. This would have a rippling effect when everyone shifts on the scale because there would not be as many people going into the old age category.

Other issues, like a pandemic, could also influence how the population ages by affecting old people the strongest. It is an unfortunate aspect of getting older that your body does not fight off diseases as well, and you are more likely to have serious complications, like getting sick. This would decrease the graying of a country by some degree.

Migration is the rate of individuals leaving or entering a country. This can be a coming or a going concern. Because I am not up to date on current migration policies, let's just use an example of two countries: A and B. Let's say everyone loves country B. People from country A will emigrate out of country A. The people migrating typically are middle aged and younger people, leaving an older population in country A.

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