Let's look now at the age profile of the world population. What you can see here are a number of curves, which are referred to as population pyramids. I've got six of them here for six different countries and you can see that
Let's look now at the age profile of the world population. What you can see here are a number of curves, which are referred to as population pyramids. I've got six of them here for six different countries and you can see that they have quite different shapes. On the left hand side of each pyramid, we have a distribution of the age of males. On the right hand side, we have the age distribution of females.
Let's look at the population pyramid for Australia. What we can see is that perhaps past the age of sixty, the population of both males and females starts to taper off and that's essentially, the effect of people dying of old age. You can see that around the age of thirty to thirty five, there is a bit of a bump in the population and that would reflect either a spike in the birth rate thirty to thirty five years ago or perhaps, a surge in immigration into the country.
If we look at the population pyramid for Japan, we see that it has a very, very different shape indeed. We can see a taper down here and what that indicates is that the birth rate in the country is falling off. We can also see that the Japanese are very long lived. There are many more people aged above eighty than there are in Australia. We can also see that there is this large area of people aged above effectively forty-five. This means that they have quite a large proportion of elderly people in their society with not too many young people coming in to replace them.
The curve for Germany, you can see it's also quite different. It's got this big bulge in the range fifty to sixty which indicates something about a population boom that started nearly sixty years ago.
The population pyramid for China has got a number of quite interesting lumps and bumps, which probably reflect many events in the history of that country.
The population pyramid for India also has a very unique shape and effectively, represents the fact that the life expectancy in India is much less than it is in countries such as Australia, Germany, United States or Japan.
Now, what I'm going to do is to highlight a band of ages, the ages between twenty and sixty. These are working aged people in these societies. So, people less than twenty are generally being supported by their parents. They're typically at school or at university. Those above sixty have retired and are being supported either by the state or by their children.
So, a really important concept in understanding populations is what’s called the dependency ratio; that's the ratio of the number of dependents, that's children and older people to the number of workers, the people who are earning a salary, doing a job and supporting the young and the old people.
For dependency ratio, a low value is good. The dependency ratios that are plotted here are for Australia and we can see that they achieved a minimum in the year 2010, that's when the dependency ratio was the best it could possibly be. As we move forward in time, the dependency ratio grows. In fact, it gets worse, that 