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AP Human Geography
Unit 2 Overview: Population and Migration Patterns and Processes
2.1 Population & Migration
2.2 Consequences of Population Distribution
2.3 Population Composition
2.4 Population Dynamics
2.5 The Demographic Transition Model
2.6 Malthusian Theory and Geography
2.7 Population Policies
2.8 Women and Demographic Change
2.9 Aging Populations
2.10 Push and Pull Factors in Migration
2.11 Forced vs. Voluntary Migration
2.12 Effects of Migration

🚜ap human geography review

2.5 The Demographic Transition Model

Verified for the 2025 AP Human Geography exam•Last Updated on June 18, 2024

Demographic Transition Model

Definition: The Demographic Transition Model (apprev. DTM) has five stages that can be used to explain population increases or decreases. The DTM is a key tool for understanding global and regional population dynamics. You need to be able to recognize the 5 stages of the DTM when looking at a population pyramid.

Stage 1

Stage one of the DTM has a high birth rate and a high death rate. Because of this, the natural increase rate is close to zero. Zero population growth is when the crude birth rate and crude death rate are equal and the population remains the same. The birth rate and the death rate are both high and equal to each other.

No official country in the world is currently in stage 1. There may be small communities of humans that are in stage 1 of the DTM. Some Indigenous groups in the Amazon or Sub-Saharan Africa are in stage one, but not all pre-contact Indigenous peoples have high birth rates and high death rates. 

For 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. Remember that it took the world about 100,000 years to reach one billion people! 

Stage 2

Stage two is the early expanding stage where the population begins to rise. It has a high birth rate, but the death rate drops. Because of this, the natural increase in population rate goes way up! Infant death rates are often high in stage 2 communities but people who do survive birth live longer. A key feature of stage 2 of the Demographic Transition Model is the emergence of grandparents. Longer life expectancies allow for 3 generations to share a part of their life spans. Grandparents are part of every stage of the DTM but will be rare in societies with shorter life expectancies.

Identify stage 2 of the DTM on a population pyramid. A number of countries in Sub-Saharan Africa (Niger, Democratic Republic of the Congo, Somalia) are currently in stage two. This is the population pyramid for Niger from 2019. The population of Stage 2 countries is rising and their doubling time is short. However, the population will not continue to go up at the same rate.

The population pyramids of these countries have a very wide base that gets thinner and thinner the higher you go.

➕Population of Niger

Stage 3

Stage three is the late expanding stage. The birth rate goes down, while the death rate remains low. The population continues to grow, but not nearly as quickly as stage two because 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. Stage three countries start to become more industrialized, which means they are more urbanized and the total fertility rate goes down. Countries that are currently in stage three are 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.

➕Population of Mexico

Stage 4

Stage four is the low stationary phase. With countries in stage 4, the birth rates get lower, while death rates start to rise as people are getting 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 that it has every year. Other countries currently in stage four are China, Brazil, and Argentina.

The population pyramids of these countries are even throughout the age groups and somewhat resemble a skyscraper.

➕Population of Australia

Stage 5

In Stage five, countries the birth rates remain low, and the death rates go up. Because of this, 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 are 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.

➕Population of Japan

🎥 Watch: AP HUG - Deconstructing the DTM

Epidemiological Transition Model

The ETM describes the causes of death in each stage of the DTM. The Epidemiological Transition Model focuses on why death rates are high or low. 

Stage 1

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.

Stage 2

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.

Stage 3

People are living much longer. However, chronic diseases associated with age become a challenge. Things like cancer and heart disease are the leading causes of death. 

Stage 4

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

Stage 5

Stage five has the highest death rates because the population is older. This leads to a negative NIR. 

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.

🎥 Watch: AP HUG - Population Growth and Decline

Key Terms to Review (32)

Cancer and heart disease: Cancer and heart disease are major causes of morbidity and mortality worldwide, representing significant public health challenges. Both conditions are often associated with lifestyle factors, environmental influences, and genetic predispositions, impacting population health across various demographic stages. Their prevalence can be influenced by the demographic transition model, as societies move from high to low mortality rates, shifting the focus of health concerns from infectious diseases to chronic conditions.
Chronic diseases associated with age: Chronic diseases associated with age refer to long-term health conditions that become more prevalent as individuals grow older, such as heart disease, diabetes, and Alzheimer's disease. These diseases often require ongoing medical attention and can significantly impact the quality of life. As populations age, the prevalence of these diseases increases, influencing healthcare systems, economic resources, and social structures.
Disease evolution: Disease evolution refers to the process by which pathogens, such as bacteria and viruses, change over time through genetic mutations and adaptations. This process can significantly impact human health, as evolving diseases may become more virulent or resistant to treatments, influencing patterns of morbidity and mortality in populations. Understanding disease evolution is crucial in the context of demographic changes and public health responses.
Doubling Time: Doubling time is the period it takes for a population to double in size, assuming a constant rate of growth. It’s a critical concept in understanding population dynamics and can indicate how quickly a population is expanding, which can have various social, economic, and environmental implications. This term is closely linked to the demographic transition model as it reflects how changes in birth and death rates influence population growth rates over time.
End to Warfare: The End to Warfare refers to the cessation of large-scale conflicts and military hostilities, which can lead to significant shifts in demographic patterns, economic development, and social structures. This concept is particularly relevant in understanding how societies transition through various stages of development, ultimately fostering peace, stability, and population growth.
Environmental Factors: Environmental factors refer to the physical characteristics of a location that influence human activities and societal development, including climate, topography, vegetation, and natural resources. These factors play a significant role in shaping population distribution, migration patterns, and cultural diffusion, affecting everything from agricultural practices to urban settlement and economic growth.
Epidemiological Transition Model: The Epidemiological Transition Model describes the changing patterns of health and disease in a population as it transitions through different stages of development. This model outlines how societies evolve from facing epidemics and pandemics of infectious diseases to experiencing chronic diseases and lifestyle-related health issues as they progress economically and socially. Understanding this model helps to connect demographic changes, the consequences of where people live, and the dynamics of population growth and decline.
Graying Populations: Graying populations refer to the increasing proportion of older individuals within a society, often resulting from declining birth rates and increased life expectancy. This demographic shift has profound implications on social services, healthcare systems, and economic structures as societies adapt to a larger elderly demographic.
Improved Sanitation: Improved sanitation refers to the access to facilities and services that safely manage human waste and promote hygiene, which significantly contributes to public health. This concept encompasses various interventions, such as proper sewage disposal systems, clean drinking water sources, and adequate waste management practices. Enhanced sanitation reduces the prevalence of waterborne diseases, improves overall health outcomes, and is a critical factor in population growth and demographic changes.
Increased connections: Increased connections refer to the growing interdependence and interaction among people, places, and ideas, often facilitated by advancements in technology and communication. This concept is particularly relevant in understanding demographic trends, as it highlights how improved transportation, globalization, and migration patterns affect population dynamics and societal changes over time.
Industrialized: Industrialized refers to the process by which a society transforms from an agrarian-based economy to one dominated by industry and manufacturing. This shift often leads to significant changes in economic structures, social systems, and urban development, ultimately resulting in increased production capabilities and improved standards of living.
Infant Death Rates: Infant Death Rates refer to the number of infants dying before reaching one year of age, typically expressed per 1,000 live births in a given year. This statistic serves as a critical indicator of a country's overall health care quality, socio-economic conditions, and access to necessary medical services. A high infant death rate often reflects issues like poor maternal health, inadequate nutrition, and insufficient health care systems.
Infectious Diseases: Infectious diseases are illnesses caused by pathogenic microorganisms, such as bacteria, viruses, parasites, or fungi, that can be transmitted from one individual to another. These diseases often have significant impacts on population health and mortality rates and can influence demographic trends by altering birth and death rates, especially in the earlier stages of demographic transition.
Infrastructure: Infrastructure refers to the fundamental facilities and systems that support the functioning of a society, including transportation, communication, water supply, and energy systems. It is essential for economic development, urban growth, and social well-being, connecting various elements like population distribution, urban development, and agricultural practices.
Low Stationary Phase: The Low Stationary Phase is a stage in the Demographic Transition Model where both birth and death rates are low, leading to a stable population size. This phase typically follows the Industrial Stage, and is characterized by advanced healthcare, high living standards, and an overall high quality of life that contributes to lower fertility rates. As a result, the population stabilizes rather than experiences significant growth or decline.
Natural Increase Rate: Natural Increase Rate (NIR) is the difference between the number of live births and the number of deaths in a given population over a specific period, typically expressed as a percentage. It reflects the growth or decline of a population independent of migration, playing a crucial role in understanding demographic trends and changes within societies.
Negative NIR (Net Immigration Rate): Negative NIR refers to a situation where the number of people leaving a country exceeds the number of people entering it, resulting in a net outflow of migrants. This phenomenon often indicates broader social, economic, or political issues within a country that may drive residents to seek opportunities elsewhere, impacting population growth and demographic changes.
Net-In Migration: Net-In Migration refers to the situation where the number of people moving into a specific area exceeds the number of people moving out. This phenomenon can lead to population growth and has significant implications for the social, economic, and cultural dynamics of a region. It is an important factor in understanding how populations change over time, influencing aspects such as urbanization, resource allocation, and demographic transitions.
Pandemics: Pandemics are widespread outbreaks of infectious diseases that affect a large number of people across multiple countries or continents. They often have significant impacts on public health, economies, and societal structures, leading to changes in population dynamics and governance strategies during and after their occurrence.
Parasitic Diseases: Parasitic diseases are illnesses caused by parasites, which are organisms that live on or in a host organism and obtain nutrients at the host's expense. These diseases can significantly impact human health, particularly in regions with lower economic development and inadequate healthcare infrastructure, often correlating with higher mortality rates during specific stages of the demographic transition model.
Pear Shape: Pear shape refers to a demographic pattern observed in the demographic transition model, where a country's population pyramid has a wider base and gradually narrows towards the top, indicating higher birth rates and lower death rates. This shape reflects the early stages of population growth, where there are many young people and relatively few elderly individuals, showcasing the potential for rapid population increase.
Population Pyramid: A population pyramid is a graphical representation that shows the distribution of various age groups in a population, typically divided by gender. It highlights demographic trends, indicating aspects like birth and death rates, and is crucial for understanding population dynamics, migration patterns, and the composition of a society over time.
Poverty: Poverty is the state of having insufficient financial resources to meet basic living needs, including food, shelter, and healthcare. It is closely tied to social and economic conditions, influencing population growth, urbanization patterns, and access to resources. The consequences of poverty can be seen across demographic shifts, sustainable development challenges, and gender roles in agriculture, shaping the overall health and stability of societies.
Pro-natalist Policies: Pro-natalist policies are government measures designed to encourage higher birth rates and support family growth, often implemented in response to declining population levels. These policies can include financial incentives, parental leave benefits, childcare support, and public campaigns promoting the benefits of larger families. The connection between these policies and demographic trends is critical as they seek to counteract issues such as an aging population and labor shortages.
Skyscraper shape: Skyscraper shape refers to the architectural design and form of tall buildings, characterized by their verticality and use of modern materials like steel and glass. This form reflects urbanization and population density, as cities expand upwards to accommodate growing numbers of residents and businesses in limited space.
Stage 2: Stage 2 is a phase in the Demographic Transition Model characterized by high birth rates and declining death rates, resulting in rapid population growth. This stage usually follows a pre-industrial society and is marked by improvements in healthcare, sanitation, and nutrition, which contribute to a significant drop in mortality rates while birth rates remain high. As a result, countries in this stage often experience a demographic explosion as they transition toward more industrialized economies.
Stage 4: Stage 4 of the Demographic Transition Model is characterized by low birth rates and low death rates, leading to a stabilized population. This stage typically reflects advanced industrialized countries where families tend to have fewer children, and healthcare systems are well-developed, contributing to longer life expectancies. In this stage, population growth becomes negligible or even negative, as the fertility rate falls below the replacement level.
Stage 3: Stage 3 of the Demographic Transition Model is characterized by a decline in birth rates while death rates continue to drop, leading to a significant increase in population growth. This stage typically represents societies that are becoming more urbanized and experiencing economic development, which influences family planning and social norms regarding childbearing.
Stage 5: Stage 5 is a phase in the Demographic Transition Model that describes countries experiencing a decline in population growth rates and possibly even negative growth due to low birth rates and an aging population. This stage is characterized by high life expectancy, but with birth rates that fall below death rates, leading to challenges such as labor shortages and increased healthcare costs.
Total Fertility Rate: Total Fertility Rate (TFR) is the average number of children a woman would have over her childbearing years, given current birth rates and assuming she survives through her reproductive age. It is a crucial measure for understanding population growth, as it helps indicate whether a population is replacing itself or declining. TFR is closely linked to various demographic factors, including economic conditions, societal norms, and government policies, all of which influence reproductive behavior and family planning.
Upside-down pyramid shape: The upside-down pyramid shape refers to a demographic structure characterized by a higher proportion of older individuals compared to younger ones, indicating declining birth rates and an aging population. This shape is typically associated with stages in the Demographic Transition Model where countries experience low fertility rates and increased life expectancy, leading to potential social and economic challenges.
Urbanized: Urbanized refers to the process by which rural areas transition into urban areas, characterized by an increase in population density and the growth of cities. This transformation often involves the expansion of infrastructure, services, and economic activities in these urban spaces, leading to changes in social dynamics, land use, and demographic patterns. As societies progress through different stages of development, urbanization plays a crucial role in shaping their cultural and economic landscapes.
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2.6 Malthusian Theory and Geography