 What do you think the population of India is like? Is it increasing every year or is it decreasing or is it just stuck somewhere in between neither going up nor down? Let's figure it out. Every population has males and females of different ages. Some of them are young, some are old and some are right in between them. Say we pick out some random numbers for these ages. Say that we have about hundred young people, then some 45 adults and some 13 elderly people. So if you now plot these numbers on a graph against their age groups, so that means the age group will lie on the y-axis and the numbers will lie on the x-axis. If you plot this then you will get something that looks like a pyramid, something like this. We call this an age pyramid. Age pyramid. Now we'll be talking about this age pyramid or it's also called a population pyramid. We'll be talking about this in a bit more detail in some time but it is this age or population pyramid that gives us the necessary information to predict the status of a population, especially the shape of the pyramid. It tells us whether a population is growing or shrinking or whether it's going to stay constant. It also tells us the rates at which people are being born or the rates at which the people are dying, then how long you can expect the members of the population to live and the rate at which the population, the entire population is changing. But how can the shape of anything possibly give us all of this information, possibly tell us so much? I looked up on the internet and found this age pyramid of Nigeria for the year 2020. What kind of shape do you think you see over here? I mean it looks like a pretty neat pyramid to me because we have a really broad base over here and then we have this tapering top right over here but what does it even mean to have a broad base or a tapering top? Okay so we already know which axis has what. The x-axis has all the individual numbers. In this case however these are in percentage and we'll get to this in just a minute why it's percentage and not whole numbers. The y-axis on the other hand has all the age groups going from young to old. There's one more thing going on in this graph and it is this divide right in the middle. Half of it is colored in blue and the remaining half is in pink. This denotes the males and females of the population and these are the percentages of sex ratios. The blue part talks about the percentage of males in the population and the pink part talks about the percentage of females in the population and the reason why we go ahead with percentage is that it makes it easier for us to interpret the data. Think about it. Is 8.4% easier or 17,377,486? Definitely 8.4% because the other number is almost like a phone number. Right at the bottom are the young ones who cannot reproduce or the pre-reproductive ages. Right in the middle there are the adults who can reproduce so they make up the reproductive ages and from ages 45 and up they become the post-reproductive group which involves all of the elderly people or the older people, the grandparents of the population you can say. Now let's go back to our original question. What does a broader base mean? At the base or at the bottom we have the young ones who cannot reproduce so a broader base indicates a large number of young ones. Similarly at the top we have the older age groups and a tapering top means that there is a much lesser number of elderly men and women. So what will the future look like for a present with a lot of younglings and less elderly? The younglings will eventually grow to reproduce and give birth to more babies. The absolutely elder ones they will eventually perish and the people in their middle ages whose numbers are pretty low compared to the numbers of the young population, the younger ones. They will eventually grow old and move closer to death. So that means that more babies will be born and comparatively less people will grow old and die. So this population will eventually increase. This is an increasing population. It will expand. So we can say that Nigeria's population is expanding and this type of an age pyramid we call it the expanding age pyramid. So this is an expanding type of age pyramid. Even this tiny pyramid that we had drawn earlier is an expanding type of an age pyramid because the number of because there are so many more younger people compared to the older people. So that is why this is an expanding age pyramid and generally you will find this trend a lot in the developing nations of Africa like Ghana or Angola and all of these countries. In those countries this is the trend right now. It's an expanding population. Now Nigeria isn't the only country that I looked up when I was reading up about this. This is Italy in the year 2020 and this looks nothing like the other one. That other one was such a pretty pyramid. This I'm not even entirely sure what this shape is supposed to be. But if you look at the base and then at the top then it kind of looks like an urn because the base is not that broad and then it starts to get broad in the middle before it eventually tapers slowly and becomes tiny. A not so broad base indicates that the number of younger ones in the population is much less and a broader middle means that comparatively there's a much higher number of reproducing adults. Now what could this possibly mean? It would mean that in the future there will be fewer people reproducing because these young ones are already very less in number right. So they will eventually grow up and they will be the reproducing adults. Meanwhile the more the larger number of reproducing adults that we had they would eventually grow old and there will be a higher number of people becoming old and moving closer to death. So that means more number of people will eventually get old and die and less number of people will be born because the number of reproducing adults is already less. So in that way this population will not grow at all. In fact this population will start to shrink or this population is already shrinking or it's declining. So this type of an age pyramid we call this a declining or you can also call it a constrictive age pyramid and it turns out that most industrialized developed countries are facing this kind of a trend or they have this type of a trend like Germany and Japan. Now to be honest I kind of got carried away and ended up looking at the graphs of way too many countries and that's how I came across this one. This is Argentina in the year 2020 the population of Argentina and over here this is unlike anything that we have seen so far the shape here it's kind of like a bell or you can say kind of like a barrel and that's because the number of young ones is almost the same as the number of reproducing adults. That means in the future of this population the number of young ones becoming reproducing adults will be the same as the number of reproducing adults becoming old. So that means the number of individuals who will be giving birth and increase the population basically will be the same as the number of individuals who will end up dying. So we're adding new members to the population but at the same time more members are kind of getting out of the population. So there won't be any kind of change in this population at all. It's like as if this population is constant, stable and that is what this is. This is a stable or a stationary age pyramid. This is a stable or a stationary age pyramid and you will find this trend in both the United States as well as Canada. Both of them have a stable or a stationary age pyramid or a population pyramid. How about we take a look at India now? That's how we started off this video right? We wanted to know what the population of India looks like. So this is what I found. This is the population pyramid or the age pyramid of India in the year 2020. Now what kind of trend can you see over here? At the first glance it seemed like India has a stable population because the age pyramid is shaped like a barrel and the number of young ones, the non reproducing young ones, they are almost quite similar to the number of the reproducing adults. So it made sense to think of this as a stable population. But then I decided to look a little bit closely. Now notice the base right over here. If you notice carefully you will see that the number of young ones is slightly less compared to the number of reproducing adults. There's a slight decrease over here. They're not quite the same. It's not by a lot. The decrease is not by a lot but it's definitely there. It's not like how we saw it in the Argentina graph. So we can say that the Indian population may look like it's stable but chances are that it might start to decline in the near future and that is indicated by this decrease right over here that we just talked about. But all of these predictions are not set in stone. Population size differs from year to year. Nobody saw the COVID pandemic coming and an event like that severely affects the status of a population and not just for people but for any organism out there. Several factors can affect the direction in which a population is headed. Always remember that an age pyramid allows us to predict not confirm.