This is the demographic transition model, and this is what you look like trying to understand it. But buck up, my dear people, because by the end of this video you're going to understand everything you need to know about this thing. And bonus, I'll tell you about another explanation for demographic change called the epidemiological transition theory.
So if you're ready to get them brain cows milked, let's get to it. Okay, first things first, why do you even have to learn this graph? Like what is it supposed to explain? Well over the last few videos we've been talking about how populations grow and decline and the demographic transition model tries to answer the question of why these patterns of growth and decline occur over the course of history. Like, countries don't just go to sleep one night and wake up the next morning like, Oh, nip!
We just doubled our population! Let's build some schools! No, there are many factors that influence population growth and decline, and that's what this model seeks to explain.
In the demographic transition model, known by its nastier abbreviation, DTM argues that changing birth rates and and death rates can be explained by a country's level of development from agrarian to industrial over time. And before I explain exactly what that means, let me just mention to you that if you need help getting an A in your class and a 5 on your exam in May, then you might want to check out my AP Human Geography Heimler Review Guide. It's got whole unit review videos that you're not going to find here on YouTube, it's got note guides to follow along, practice questions, practice exams, and answer keys for all of it.
So if that's something that you're into, check out the link in the description. Okay, now before we get into the details of the DTM, it might help to break this whole mess down into individual parts. These five boxes represent historical stages, starting with agrarian or farming societies here, and then moving to developed industrial societies here. Now, this line right here shows us the total population as a country moves through these stages, and over time the population is growing until stage 5 where it starts declining. again.
Okay, so all we're seeing here is that as a country goes through these five stages of development, population increases until that very last stage. Now the question is, why does a population do that in response to these stages? Well, let's add another layer, this time the birth rate, which looks like the opposite of the population curve. And that doesn't make any sense, right? Like if lots of babies are being born, then why is the total population so low over here?
And if relatively few babies are being born here, then why is the population so high? A fine question, and I shall answer presently by introducing the last element of this model, namely death rates. And with that we can go through the various stages. Stage one is known as the high stationary stage, and a society in this phase is pre-industrial and organizes its life around farming.
So yes, the birth rate is high, but so is the death rate. So they basically cancel each other out. Lots of people born, but also lots of people living short lives and dying, so the population remains stable or shows slight increases or decreases.
As we stand today, no present country exists since stage one. But then we move to stage two, which is known as the early expanding stage, which corresponds to the beginnings of industrialization. For example, England in the mid-18th century was here as they transitioned from agrarian production to building factories all over the dang place and selling their goods on the world market.
And here the birth rate remains high, but the death rate drops like a rock because with industrialization comes new medical technology, access to better food and vaccinations, etc. So because all of that is now available, it means people are living longer lives. But since they haven't slowed down on having lots of babies, what we see here is a population explosion. And it probably won't surprise you if you've been with me these last couple of videos, but today many countries in Sub-Saharan Africa are in this stage. And then we get to stage three, known as the late expanding stage, which is characterized by continuing industrialization and growing economic...
Here the birth rates begin to decline fast, but still there are more births than deaths, and so the population grows slowly. And today, many developing nations are in this stage. But moving along to stage 4, and we're in the low stationary stage, and here a country is completely industrialized. Birth rates and death rates are pretty close to each other, which leads to slow growth or stabilization in the population. And because people are living so much longer in this phase, they've got new worries about aging populations, like diseases of old age and care for the elderly.
And today, most developed nations are in this stage. And finally, we get to stage 5, which wasn't part of the original model, but has been added more recently to reflect declining populations, which is why it's called the Natural Decrease Stage. Here, the death rate exceeds the birth rate, and so the rate of natural increase begins to decline. And an example of a country in this phase is Japan. Don't worry.
Don't worry guys, you're doing great. Believe in yourself. Okay, so that's one explanation for how populations transition through history by considering birth and death rates as related to a country's level of industrialization. But before we move on, let me make note of two things you need to remember. First, this model only considers demographic transition through the lens of birth and death rates, but that's not the whole picture in the real world.
In the real world, populations often grow or decline through migration as well. And then second, this model was developed in the early 20th century to explain population trends in Western countries, and that means its explanations might not apply to how countries develop in the modern world. world elsewhere. Okay, now let's consider a second framework that explains demographic transition called the epidemiological transition model.
And this model explains demographic transition, not with levels of industrialization and development, but through the lens of disease and the death rate. And that's what epidemiology is. It's the study of how diseases spread.
So through this lens, stage one is the famine stage. And here the death rate is high and people are dying all over the dang place from just about anything that you can imagine dying from, like infectious diseases or poor nutrition or... bear attacks, whatever.
So that means in this stage, life expectancy is low. And although a population can grow, it usually is in small bursts and is not sustained. But then we get to stage two, which is the receding pandemic stage where life expectancy The increase is significantly from about 30 years old to the ripe old age of 50, and therefore death rates decrease. A population enters this stage because they figured out better methods of sanitation, and they have expanded access to various nutritious foods, and they have new medicines to help fight off diseases.
But it's not all puppies and rainbows here, because in this phase, people are mainly dying in large numbers from pandemics, which are diseases that spread throughout whole regions. And this is especially true because people in this phase are living much closer together in cities where diseases like cholera spread like mad. And then comes stage three, which is called the degenerative and human-created disease stage.
Here life expectancy increases even more, and that sounds great, but aging populations have new problems. Here people are dying not so much from infectious diseases, but from diseases of old age, like heart disease or cancer. Even so, the death rate is low and life expectancy continues to increase. And then comes stage 4, which is called the delayed degenerative disease stage.
Here, life expectancy is at its highest because all those pesky diseases from the third stage now have effective medical interventions. Like for heart disease, you get bypass surgery. Or for cancer, you have radiation and chemotherapy. And finally, the fifth stage in the ETM is a profound bummer, namely the re-emergence of infectious disease stage.
Like remember all those infectious diseases we cured back in stage three? Well, they went away, stroked their mustaches, and plotted their revenge. And here in stage five, they come right on back, having leveled up by developing immunity to our drugs and antibiotics.
And in that way, infectious diseases become deadly once again and life expectancy decreases. Okay, last thing. As with the DTM, the ETM has some significant weaknesses. First of all, it's an oversimplification of demographic change based ONLY on death rates and disease.
Second, the ETM doesn't account for poverty as a significant cause for the spread of disease. And honestly, poverty is one of the most significant causes of shortened lifespans and probably does a better job explaining the differences in death rates than the spread of disease. disease.
Okay, click here to keep reviewing my other Unit 2 topic videos, and click here to grab my AP Human Geography Heimler Review Guide, which has everything you need to get an A in your class and a 5 on your exam in May. I'll catch you on the flip-flop. Heimler out.