Demographic Transition Model in Detail
This lesson provides a thorough analysis of the Demographic Transition Model (DTM), covering all five stages, the drivers behind changing birth and death rates, natural increase and decrease, population pyramids, dependency ratios, and the concepts of the demographic dividend and demographic time bomb. This content is essential for AQA A-Level Geography Paper 2, Section C.
What Is the Demographic Transition Model?
The Demographic Transition Model (DTM) describes how a country's population changes over time as it develops economically. It was first proposed by Warren Thompson (1929) and later refined by Frank Notestein (1945). The model links economic development to shifts in birth rates, death rates, and overall population growth.
The DTM is divided into five stages, each characterised by different combinations of crude birth rate (CBR), crude death rate (CDR), and rate of natural increase (RNI).
Key Definition: The rate of natural increase (RNI) is the difference between the crude birth rate and the crude death rate, expressed as a percentage: RNI = (CBR − CDR) / 10.
Key Population Measures
| Measure | Definition | Typical Formula |
|---|
| Crude Birth Rate (CBR) | Live births per 1,000 people per year | (Live births ÷ Total population) × 1,000 |
| Crude Death Rate (CDR) | Deaths per 1,000 people per year | (Deaths ÷ Total population) × 1,000 |
| Total Fertility Rate (TFR) | Average children born per woman over her lifetime | Sum of age-specific fertility rates |
| Infant Mortality Rate (IMR) | Deaths of infants under 1 year per 1,000 live births | (Infant deaths ÷ Live births) × 1,000 |
| Life Expectancy | Average years a newborn is expected to live | Derived from mortality tables |
| Replacement-level Fertility | TFR needed to maintain population size | Approximately 2.1 in developed countries |
Stage 1: High Stationary
- CBR: Very high (35–50 per 1,000)
- CDR: Very high (35–50 per 1,000)
- Natural Increase: Very low or zero
- Population Growth: Stable, fluctuating
Characteristics
- No modern medicine or sanitation; high infant mortality rates (often above 200 per 1,000)
- Famines, epidemics, and warfare cause periodic spikes in the death rate
- No access to contraception; children are an economic asset (labour on farms)
- Religious and cultural norms encourage large families
- Life expectancy is typically below 40 years
Case Study
No country today sits firmly in Stage 1. Pre-industrial England (before 1750) and isolated indigenous communities historically exhibited Stage 1 characteristics. Archaeological evidence from medieval Europe shows CDRs periodically exceeding 100 per 1,000 during plague years.
Stage 2: Early Expanding
- CBR: Remains high (35–50 per 1,000)
- CDR: Falls rapidly (15–35 per 1,000)
- Natural Increase: Rapid population growth
- Population Growth: Accelerating
Drivers of Falling Death Rates
- Improved sanitation and clean water — sewage systems, piped water reduce waterborne diseases
- Medical advances — vaccination programmes, antibiotics, hospitals
- Better nutrition — agricultural improvements (e.g., crop rotation, new crops)
- Public health measures — quarantine, health education
- Political stability — reduced warfare, better governance
Why Birth Rates Remain High
- Cultural lag: attitudes to family size change slowly
- Children still seen as economic assets and old-age insurance
- Limited access to contraception and family planning education
- Religious opposition to birth control persists
- High infant mortality means parents have extra children as insurance
Case Study: Sub-Saharan Africa
Many sub-Saharan African nations are in Stage 2. Niger has a TFR of approximately 6.7 (2023), one of the highest globally. CDR has fallen from around 30 in the 1960s to approximately 11, driven by vaccination campaigns and improved healthcare. However, CBR remains above 45, leading to a population growth rate exceeding 3.7% per year — the population doubles roughly every 19 years.
Stage 3: Late Expanding
- CBR: Falling (15–35 per 1,000)
- CDR: Low and stable (10–15 per 1,000)
- Natural Increase: Moderate but declining
- Population Growth: Slowing
Drivers of Falling Birth Rates
- Urbanisation — children become an economic cost rather than an asset
- Female education and empowerment — educated women tend to delay marriage and have fewer children
- Access to contraception — family planning clinics, availability of the pill and condoms
- Declining infant mortality — fewer children die, so parents have fewer
- Government policies — incentives for smaller families
- Changing social values — desire for consumer goods, career aspirations
Case Study: India
India transitioned through Stage 3 from the 1970s onwards. The TFR fell from 5.9 in 1970 to approximately 2.0 by 2023 — below replacement level. Key factors include increased female literacy (from 22% in 1971 to over 70% by 2021), government family planning programmes, and rapid urbanisation. However, significant regional variation exists: states such as Bihar and Uttar Pradesh have higher fertility rates than Kerala and Tamil Nadu.
Stage 4: Low Stationary
- CBR: Low (10–15 per 1,000)
- CDR: Low (10–15 per 1,000)
- Natural Increase: Very low or zero
- Population Growth: Stable or very slow
Characteristics
- Post-industrial economies with high living standards
- Women participate fully in the workforce
- Contraception is widely available and socially accepted
- High cost of raising children (education, housing, childcare)
- Delayed marriage and childbearing; average age of first birth often above 30
- Population growth primarily from immigration rather than natural increase
Case Study: United Kingdom
The UK is firmly in Stage 4. The TFR was approximately 1.49 in 2022, well below replacement level. The CBR is around 10 per 1,000 and the CDR around 10 per 1,000. Population growth of approximately 0.5% per year is driven largely by net migration rather than natural increase. The average age of mothers at first birth rose from 24 in 1970 to over 30 by 2022.
Stage 5: Declining
- CBR: Very low (below 10 per 1,000)
- CDR: Exceeds CBR (10–15 per 1,000)
- Natural Increase: Negative (natural decrease)
- Population Growth: Declining without immigration
Characteristics
- Sub-replacement fertility (TFR well below 2.1)
- Ageing population with rising median age
- Increasing old-age dependency ratio
- Growing demand for healthcare and pensions
- Labour shortages in key sectors
- Government pro-natalist policies often introduced
Case Study: Japan
Japan is the most frequently cited Stage 5 example. The TFR fell to approximately 1.20 in 2023 — one of the lowest globally. The population peaked at 128.1 million in 2010 and has since been declining, falling to approximately 124.5 million by 2023. Over 29% of the population is aged 65 or above. The Japanese government has introduced various pro-natalist policies, including childcare subsidies and parental leave, but with limited success. Without significant immigration, the population is projected to fall below 100 million by 2050.
Age-Sex Pyramids
Population pyramids (age-sex pyramids) are graphical representations of the age and sex structure of a population. They provide a visual snapshot of a country's demographic profile.
Pyramid Shapes by DTM Stage
| Shape | DTM Stage | Characteristics | Example |
|---|
| Wide base, narrow top (triangular) | Stage 2 | High birth rate, high death rate, low life expectancy | Niger, Mali |
| Narrowing base, bulging middle | Stage 3 | Falling birth rate, growing working-age population | India, Brazil |
| Column-shaped (even sides) | Stage 4 | Low birth and death rates, balanced age structure | UK, France |
| Inverted triangle (narrow base, wide top) | Stage 5 | Very low birth rate, ageing population | Japan, Germany |
Reading Population Pyramids
- Wide base indicates high birth rates and a youthful population
- Narrow base indicates low birth rates and potential population decline
- Bulges may indicate baby booms or immigration of working-age adults
- Indentations may indicate wars, famines, emigration, or disease outbreaks
- Asymmetry between males and females may reflect gender-selective migration or differential mortality
Dependency Ratios
The dependency ratio measures the proportion of dependants (those not of working age) relative to the working-age population.
Formulae
- Total Dependency Ratio = ((Population 0–14) + (Population 65+)) ÷ (Population 15–64) × 100
- Youth Dependency Ratio = (Population 0–14) ÷ (Population 15–64) × 100
- Old-Age Dependency Ratio = (Population 65+) ÷ (Population 15–64) × 100
Implications
| High Youth Dependency | High Old-Age Dependency |
|---|
| Greater spending on education and childcare | Greater spending on healthcare and pensions |
| Potential for future demographic dividend | Labour shortages and reduced economic output |
| Strain on family resources | Increased tax burden on working population |
| Common in Stage 2/3 countries | Common in Stage 4/5 countries |
The Demographic Dividend
The demographic dividend occurs when a country's working-age population grows larger relative to dependants, creating a window of economic opportunity.
- Typically occurs during Stage 3 of the DTM
- A large working-age cohort can boost economic productivity, savings, and investment
- This dividend is not automatic — it requires investment in education, healthcare, and job creation
Case Study: South Korea
South Korea experienced a dramatic demographic dividend from the 1960s to 2000s. As fertility fell from a TFR of 6.0 in 1960 to 1.5 by 2000, the working-age population grew rapidly. Combined with heavy investment in education and export-oriented industrialisation, GDP per capita rose from approximately 160in1960toover30,000 by 2020.
The Demographic Time Bomb
The demographic time bomb refers to the challenges posed by an ageing population when the dependency ratio rises sharply.
- Fewer workers supporting a growing number of retirees
- Pension systems become unsustainable
- Healthcare costs escalate as demand for geriatric care increases
- Economic growth slows due to a shrinking labour force
Policy Responses
- Raise retirement age — many European countries have raised the state pension age to 67 or 68
- Pro-natalist policies — financial incentives for having children (e.g., France's family allowances)
- Encourage immigration — to replenish the working-age population (e.g., Germany post-2015)
- Increase workforce participation — particularly among women and older workers
- Invest in automation — to maintain productivity with fewer workers
Evaluation of the DTM
Strengths
- Provides a useful framework for understanding population change over time
- Based on the historical experience of European countries
- Helps predict future population trends and plan accordingly
- Identifies links between economic development and demographic change
Limitations
- Based on Western European experience — may not apply to all countries
- Assumes all countries will follow the same trajectory
- Does not account for the impact of migration
- Does not explain the speed of transition (which varies greatly)
- Stage 5 was added later and remains debated
- Cannot predict the impact of pandemics (e.g., HIV/AIDS in sub-Saharan Africa reversed CDR declines)
- Oversimplifies — internal regional variations are often significant
Exam Tip: When using the DTM in exam responses, always acknowledge its limitations. Examiners reward critical evaluation. Use specific data and case studies to support your points rather than making general statements.
Summary
- The DTM describes population change through five stages linked to economic development
- Birth and death rates are driven by a complex interplay of social, economic, cultural, and political factors
- Population pyramids visually represent age-sex structure and help identify demographic challenges
- Dependency ratios quantify the economic burden of non-working populations
- The demographic dividend offers economic opportunity during Stage 3, while the demographic time bomb threatens Stage 4/5 countries
- The DTM is a useful but imperfect model that must be applied critically with case study evidence