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Malthusian Theory and Demographic Transition Theory

Malthusian Theory and Demographic Transition Theory

Author: Paul Hannan

Identify the main ideas comprising theories of population growth.

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Source: Intro Music by Mark Hannan; Public Domain

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[MUSIC PLAYING] Welcome to this episode of Sociology, Studies of Society. Today's lesson is on Malthusian theory and demographic transitional theory. As always, don't be afraid to pause, stop, rewind, or even fast forward to make sure you get the most from this tutorial.

So today we're looking at two different theories on population growth, and how that affects the world and societies. So before we look at those actual two theories, I just want to give you two terms that will help us when we're looking at some graphs here. So the first one is sex ratio. And that's just a ratio that's looking at the relative number of females to males within any group or population.

And the second one is population pyramid, and that's something that's graphically breaking down a population by sex and age. Let me show you what those actually mean. It's a lot easier to see them, than just hear them.

So what you're looking at right now is a population pyramid. You have really, two different categories you're looking at. You're looking at males and females. And we're looking at them in two different ways. We're looking at how many there are and how old they are.

So the closer to the bottom of the screen, to the bottom of the graph the people are, is their age. So I don't have these categories formally made, like this person is a one to five years old. But you can tell that people at the bottom, they are young, they're the youngsters, the children. And as you go up, and it also happens to get narrower on this graph, the people at the top, those are the oldest people in society.

Now, the other thing I said we're looking at is how many people fall into these categories. So the larger the bars, the more people fall into that category. So at the very bottom for males, that is the biggest group of males. The most people are the youngest in this society. And that's also true for females. In fact, when we look at the sex ratio, there's a one to one relation for this graph and for this population. So for every male in the society, there's also one female in society.

So Malthusian theory is looking at population growth. And what it's basically arguing is this. We have food and we have people. And as we increase our population, we're also having some technological advances that are allowing us to grow more food. And that continues to grow, and it works pretty well-- at first, at least.

As populations continue to grow, we are able to have more children before we're able to support them with food. So the imagery here, what I'm trying to show is that initially, we had one stalk of corn for every two individuals. And then society grew and we still had one stalk of corn for every two individuals.

And then, the third time, all of a sudden we now have eight individuals, but only three stalks of corn. And then now it's getting worse and this theory argues that it is going to continue to get worse, and eventually, there's no way we can sustain our population and our population growth, and sustain the amount of food we need. So it's going to throw society into total chaos, and there's going to be major problems.

Now before we look at the other theory, let me explain where the other theory is really coming from. So here are some more population pyramids. And the two at the top are populations that are growing. And those really fit really well into that Malthusian theory, that we're going to keep growing populations, and the food's not going to be able to keep up.

But it's not true that every population is growing. At the bottom or two populations that are not growing, we have a stable population, we have a contracting population. So in a stable population, there's pretty much the same amount of people that are staying in that society that are being born or coming in, versus the number of people who are leaving that society, people that are dying or moving out of the population.

Then there's also a contracting population. So here there are actually more people dying than kids being born. That's why the graph is so narrow at the bottom there, because there's not very many children. And different countries are going to fall into different categories. What you are seeing right now around the world is that you're seeing a lot of the developed nations, and a lot of the high income nations, they're actually contracting in population. And a lot of the nations that are low income nations, they're going through this huge population boom, where there's tons of kids being born, and so the populations are really growing.

So this next theory really tries to account for that. So before we get into theory, let's just look at what the graph is telling us. The red line is death rate, so that's the number of people that are dying in a society. And the blue line is birth rate, and that's the number of people that are being born in this society. And this whole theory is really looking at how technology plays a part in society.

So in stage one is when societies have minimal technology. And what's happening is there's a really high birth rate, but there's also a really high death rate. So population is basically staying steady, or maybe a tiny bit rising. Then all of a sudden, we have stage two. And there's huge technological changes. And what's happening is that the birth rate is still high, but health care and different changes, the way that we're making food is getting way better. So all of a sudden, the death rate drops super, super low.

Now the next stage is stage three. And in this stage, it's arguing that society, the birth rate is now going to lower. After technology reaches a certain rate, society changes that we just don't have as many kids anymore. And then lastly, it's stage four. And this is where we come back to the equilibrium where really, about the same lot of people are dying as being born, so the population is being stable. So it's not predicting total chaos like the Malthusian theory is.

Now I'm going to add a line onto this, hopefully not confusing you, but this is looking at population. And so as we look at this here, population is slowly growing in stage one. In stage two, it takes a huge jump because technology is taking a huge jump, which is changing our life expectancy and so more people are able to live, and less people are dying every year. Stage three, that's continuing. And then I have the question mark at the end, because we haven't really seen what's going to happen at this year.

We have a couple nations that have declining birth rates, who are kind of fitting the trend. But we haven't really seen as a world, if that's going to happen. Is population going to stabilize, or is this line, instead of bending down, is it instead going to continue up and have population continue to grow? And that's the demographic transitional theory.

So today's takeaway message, we looked at the Malthusian theory and the demographic transitional theory. The Malthusian theory is that one that it's going to have this rapid population increase, and eventually it's going to outpace our food production, it's going to be total chaos. And then the demographic transition theory, which is really looking at how progress for populations and population growth really changes with how much technology a society has. And so there's not this catastrophic prediction with the demographic transitional theory.

And then at the very beginning I'd given you two terms to help us understand that, and that's sex ratio and population pyramid. Again, the sex ratio is the number of males and females within a population, relative number of males to females in a population. And the population pyramid is just a graphical way of looking at a population by its sex and age. That's it for this lesson, good work, and hopefully you'll be seeing me on your screen again soon.

Terms to Know
Demographic Transition Theory

A theory of population growth that argues that population growth varies as society progresses technologically.

Malthusian Theory

A theory of population growth that argues that rapid population growth increases would outpace food production leading to social chaos.

Population Pyramid

This pyramid graphically represents a population broken down by age and sex.


A way to express the number of males relative to the number of females in a population.