DTM MODEL

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big idea is that countries do not all grow in the same way. Some countries have very fast population growth, while others have slow growth or even population decline, and the Demographic Transition Model (DTM) helps explain why.

Demographic Transition Model

The DTM has 5 stages and shows how birth rate, death rate, and total population change over time.

  • CBR = crude birth rate.

  • CDR = crude death rate.

  • NIR = natural increase rate, which is birth rate minus death rate.

  • If CBR and CDR are both high, population growth is usually slow.

  • If CBR stays high but CDR drops, population grows very quickly.

Stage 1

Stage 1 has a high birth rate and high death rate, so population growth is low.
This stage is linked to poor sanitation, limited medicine, few contraceptives, and an agriculture-based society.
Most people in this stage work in subsistence agriculture, meaning they grow food mainly for their own use.
No countries are currently in Stage 1.

Stage 2

Stage 2 begins after the Industrial Revolution and the Medical Revolution.
Birth rates stay high, but death rates start to fall because of better medicine, sanitation, food supply, and technology.
This causes a population boom because more people are surviving.
Afghanistan is an example of a Stage 2 country.

Stage 3

In Stage 3, both birth rates and death rates start to fall.
Families begin having fewer children because cities are growing, women often have more education and rights, and children are no longer needed as much for labor.
More jobs appear in manufacturing and services, so people may choose smaller families.
Mexico is given as an example of a Stage 3 country.

Stage 4

Stage 4 has low birth rates and low death rates, so population growth is slow or near zero.
This stage often includes better health care, more education, more jobs in the tertiary sector, and higher living costs.
People tend to marry later and have fewer children.
The United States and China are examples of Stage 4 countries in the video.

Stage 5

Stage 5 is the speculative stage where the birth rate falls below the death rate.
That means the population starts shrinking over time.
Japan and Germany are examples of countries that could be in Stage 5.
It also explains that the replacement rate is a total fertility rate of about 2.1 children per woman.

Population pyramids

Population pyramids help show which stage a country is in.

  • Stage 2 pyramids are wide at the bottom because many people are young.

  • Stage 3 pyramids start to fill out in the middle.

  • Stage 4 pyramids often look box-shaped.

  • Stage 5 pyramids usually have a larger older population.

Important migration idea

birth and death rates in the DTM count only what happens inside the country.
Migration is separate, so immigration and emigration can change total population even if natural increase is low.

Epidemiological Transition Model

explains how causes of death change over time.
It has 5 stages too, and it matches population development in many ways.

Stage 1: pestilence, famine, and death

People die from infectious diseases, food shortages, dirty water, parasites, and attacks from animals.
The video mentions epidemics, pandemics, and endemic diseases:

  • Epidemic: spreads through a region or community.

  • Pandemic: spreads across many regions or the world.

  • Endemic: stays in one area.

Stage 2: receding pandemics

Deaths go down because of better medicine, more food, sanitation, and higher living standards.
This stage matches the beginning of industrialization and medical progress.

Stage 3: degenerative diseases

People live longer and start dying more from long-term diseases like heart disease or cancer.

Stage 4: delayed degenerative diseases

Medical technology helps people live longer by delaying disease.
Healthier diets and better treatment improve life expectancy, but new problems like obesity and diabetes can appear too.

Stage 5: re-emergence of infectious disease

Infectious diseases can return because of antibiotic resistance, poverty, dense cities, and globalization.
connect this to COVID-19 and the way travel spreads disease quickly.

What to remember for class

The most important thing is that the DTM shows how population growth changes as a country develops, while the epidemiological model shows how the main causes of death change over time.
A good way to study this is to remember the pattern: high birth/high death → falling death rate → falling birth rate → low growth → possible decline.