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 $160 in 1960 to over $30,000 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