AP Syllabus focus:
‘The demographic transition model can be used to explain population change over time as birth and death rates shift.’
The Demographic Transition Model (DTM) is a fundamental geographic tool explaining how populations change as societies develop, highlighting shifting birth and death rates and resulting growth patterns.
Understanding the Purpose of the Demographic Transition Model
The Demographic Transition Model (DTM) provides a structured framework for analyzing long-term population change as countries move from pre-industrial to post-industrial conditions. It emphasizes how transformations in economic development, health care, and social structures alter birth rates, death rates, and subsequently population growth. Although generalized, the model remains essential for comparing demographic patterns across regions and evaluating how development levels shape population trajectories.
Demographic Transition Model (DTM): A generalized model describing shifts in birth rates, death rates, and population growth that occur as societies industrialize and develop economically.
The model is divided into stages that illustrate predictable demographic changes associated with modernization, though real-world variations and exceptions exist.
This diagram illustrates the five stages of the demographic transition, showing how birth rates and death rates move from high to low as societies develop. The shaded area between the curves highlights natural increase and the rising total population over time. The small population pyramids beneath each stage add extra detail beyond the syllabus but reinforce long-term demographic change. Source.
These stages help geographers interpret broad patterns and compare different countries’ positions along a development spectrum.
This diagram presents a simplified version of the demographic transition, showing birth rates and death rates declining across successive stages. It emphasizes the overall pattern of shifting vital rates without including country-specific data. It focuses mainly on four classic stages, which is a minor difference from the five-stage description in the notes. Source.
Core Components of the DTM
Before examining the stages, it is important to understand the demographic variables that the model tracks.
Crude Birth Rate (CBR): The total number of live births per 1,000 people in a population per year.
A sentence must follow: The CBR provides a direct measure of how rapidly a population adds new members through childbirth.
Crude Death Rate (CDR): The total number of deaths per 1,000 people in a population per year.
Changes in these two indicators form the backbone of demographic transitions, influencing overall growth patterns.
Natural Increase: The difference between the crude birth rate and crude death rate, indicating the rate at which a population grows without migration.
This measure helps geographers understand how population size responds to shifts in the balance between births and deaths.
Stages of the Demographic Transition Model
Although the number of stages can vary by interpretation, the standard AP Human Geography approach uses five stages, each describing a distinctive combination of birth rates, death rates, and growth rates.
Stage 1: High Stationary
Pre-industrial societies fall into this stage, marked by:
High birth rates due to limited contraception, cultural norms favoring large families, and high infant mortality.
High death rates caused by poor medical care, limited sanitation, and inconsistent food supplies.
Very low population growth, as births and deaths remain in rough balance.
Few or no countries remain in Stage 1 today.
Stage 2: Early Expanding
This stage begins as societies improve living conditions.
Key characteristics include:
High birth rates remaining from traditional practices.
Rapidly falling death rates due to better sanitation, more stable food supplies, and medical advances.
Rapid population growth, often described as a population explosion.
Many least developed countries entered this stage during the 20th century.
Stage 3: Late Expanding
Industrializing societies shift into Stage 3 as social and economic changes alter reproductive behavior.
This stage features:
Declining birth rates, influenced by increased access to contraception, urbanization, women’s education, and rising costs of childrearing.
Continued decline in death rates, though at a slower pace than in Stage 2.
Slowing population growth, reflecting a narrowing gap between births and deaths.
Stage 4: Low Stationary
Highly developed countries typically fall into this stage. Key traits include:
Low birth rates driven by widespread contraception use, women’s labor participation, and lifestyle preferences.
Low death rates, supported by advanced health care and high living standards.
Very low population growth, often approaching zero population growth.
Stage 5: Declining (Proposed Stage)
Some demographers identify a fifth stage to account for recent trends:
Very low or declining birth rates, sometimes below replacement level.
Low death rates, but slightly increasing in aging societies.
Negative population growth, meaning the population shrinks without immigration.
Examples include Japan and some European countries.
How the DTM Explains Population Change Over Time
The DTM highlights the interaction between social development and demographic behavior.
This multi-panel chart compares how crude birth rates, crude death rates, and total population have changed over time in five countries. The lines reflect the demographic transition model’s pattern: mortality declines first, followed by fertility, widening the gap that drives population growth. The inclusion of specific years and countries goes slightly beyond the syllabus but offers valuable real-world context. Source.
As countries industrialize:
Improvements in public health, food production, and sanitation reduce death rates.
Changes in education, urbanization, economic structures, and women’s roles lead to declining birth rates.
Population growth accelerates, then slows, forming a demographic curve that reflects development progression.
These shifts allow geographers to analyze how and why growth patterns differ across regions and to predict future demographic challenges, such as aging populations or labor shortages. The model’s strength lies in its ability to simplify complex demographic processes into a clear, comparative framework that reveals long-term population trends shaped by changing birth and death rates.
FAQ
The model assumes that all countries follow a broadly similar path of industrialisation, urbanisation, and rising living standards, which trigger predictable changes in birth and death rates.
It also assumes access to medical advances and improved sanitation, which reduce mortality in early stages. These assumptions may not fully account for countries experiencing conflict, uneven development, or abrupt policy changes.
Birth rates tend to lag behind death rate declines because cultural norms favouring large families persist even as health conditions improve.
Additionally:
Children remain economically valuable in agrarian societies.
Access to family planning and education is often limited.
Social change typically progresses more slowly than medical or infrastructural change.
Although the model presents stages as linear, countries can experience temporary setbacks.
Reversals may occur due to:
Economic collapse
Large-scale conflict
Pandemics
Government instability
Such events can increase death rates or disrupt social structures, but long-term regression to earlier stages is uncommon.
Each stage is associated with distinct pressures on society and infrastructure.
For example:
Rapid population growth in Stage 2 may strain housing, education, and healthcare.
Low fertility in Stage 5 can lead to labour shortages and increased elderly dependency.
By locating a country’s stage, planners can anticipate future needs and policy priorities.
The model was developed using European historical experiences, which do not match all contemporary contexts.
Modern influences such as migration, government population policies, globalisation, and new medical technologies create demographic outcomes that diverge from the classic stage sequence.
Practice Questions
Question 1 (2 marks)
Describe one characteristic of a country in Stage 2 of the Demographic Transition Model.
Mark scheme (2 marks total)
1 mark for identifying a key characteristic of Stage 2 (e.g., high birth rates, rapidly falling death rates).
1 mark for explaining why this characteristic occurs (e.g., medical and sanitation improvements reduce mortality while cultural norms sustain high fertility).
Question 2 (5 marks)
Explain how changes in birth rates and death rates across the stages of the Demographic Transition Model help geographers understand patterns of population growth over time.
Mark scheme (5 marks total)
1 mark for stating that population growth depends on the gap between birth and death rates.
1–2 marks for describing how high birth and high death rates in early stages lead to low growth.
1–2 marks for explaining how falling death rates with still-high birth rates cause rapid growth in Stage 2.
1 mark for explaining that later declines in birth rates slow growth or lead to zero/negative growth.
