Demographic Transition Model Notes

The Demographic Transition Model (DTM) is a tool with five stages used to explain population increases and decreases.
It's crucial for understanding global and regional population dynamics.
You must be able to recognize the 5 stages of the DTM using a population pyramid.

Characterized by a high birth rate and a high death rate.
The natural increase rate is close to zero.
Zero population growth occurs when the crude birth rate and crude death rate are equal.
No official country is currently in stage 1.
Some Indigenous groups in the Amazon or Sub-Saharan Africa may be in stage 1.
Throughout most of human history, the entire world was in stage one.
For example, 30,000 years ago, the life expectancy of humans was around 30 years.
It took the world about 100,000 years to reach one billion people.

Early expanding stage.
The population begins to rise.
High birth rate, but the death rate drops.
The natural increase in population rate increases significantly.
Infant death rates are often high.
People who survive birth live longer.
A key feature is the emergence of grandparents as three generations share life spans.
*Countries in Sub-Saharan Africa (Niger, Democratic Republic of the Congo, Somalia) are currently in stage two
The population of Stage 2 countries is rising, and their doubling time is short.
Population pyramids in these countries have a very wide base that gets thinner.

Late expanding stage.
The birth rate goes down, while the death rate remains low.
The population continues to grow, but not as quickly as stage two.
Low births and low deaths are at equilibrium.
The natural increase rate is still positive, but not as high as in stage two.
More adults often mean more workers.
Countries start to become more industrialized, which means they are more urbanized and the total fertility rate goes down.
Countries currently in stage three: Mexico, India, Colombia, and South Africa.
The population pyramids of these countries are wider in the middle ages and have more of a pear shape.

Low stationary phase.
Birth rates get lower, while death rates start to rise as people get older.
The natural increase rates (NIR) in these countries are close to zero.
For example, in the United States, the NIR would be zero if you took away the net-in migration.
Other countries currently in stage four: China, Brazil, and Argentina.
The population pyramids of these countries are even throughout the age groups and somewhat resemble a skyscraper.

Birth rates remain low, and the death rates go up.
Countries have a negative NIR, which leads to the population decreasing.
These countries have graying populations, with fewer men and women in their childbearing years.
Countries currently in stage five: Japan and a number in Eastern Europe (Germany, Estonia, Ukraine).
Fewer young adults are having children.
Some stage 5 governments promote pro-natalist policies to try and stunt the population decrease by incentivizing having children.
The population pyramids in these countries are wider at the top and start to look like upside-down pyramids.

The ETM describes the causes of death in each stage of the DTM, focusing on why death rates are high or low.

Most people die because of pandemics, like infectious and parasitic diseases (the Black Plague and Malaria).
They will also die because of environmental factors like drought, earthquakes, floods, and also things like starvation and malnutrition.
More infants die overall.

People begin to live longer because of changes in conditions.
Changes that can move a society from stage 1 to stage 2 are improved nutrition, breakthroughs in medicine, an end to warfare, and/or improved sanitation.
In this stage, not as many people die of infectious diseases because of epidemiology, which is the branch of science that studies diseases, causes, and cures.
Because of better infrastructure (hospitals, sewers, better plumbing), fewer people die of parasitic diseases.

People are still living longer, but because of better healthcare, treatments, and medical technology people are able to survive cancer and heart disease.

Stage five has the highest death rates because the population is older.
Experts cite three different reasons for this.
- The first is disease evolution. Infectious diseases have evolved and established resistance to drugs and other treatments.
- The second is poverty. Even the most modern societies have homelessness and poverty. Infectious diseases spread more easily in these pockets of society.
- The last is increased connections. Through air travel, trains, and highways, the world is more connected than ever. Because of this, diseases like AIDS, which spread from person to person via blood or sexual fluids, can be unknowingly spread around the world.