The demographic transition model
Big idea: The demographic transition model (DTM) describes how populations change as countries develop — from high birth/death rates to low birth/death rates.
The four (or five) stages
- Stage 1 — Pre-industrial: High CBR, high CDR, low growth. No modern countries remain here.
- Stage 2 — Early expanding: High CBR, falling CDR, rapid growth. Improved healthcare/sanitation reduces deaths; births remain high. (e.g., some sub-Saharan African countries)
- Stage 3 — Late expanding: Falling CBR, low CDR, slowing growth. Education, urbanisation, and contraception reduce births. (e.g., India, Brazil)
- Stage 4 — Low stationary: Low CBR, low CDR, stable population. Typical of developed countries. (e.g., UK, USA, Australia)
- Stage 5 — Declining (contested): Very low CBR, low CDR, population decline. Ageing population, below-replacement fertility. (e.g., Japan, Germany, Italy)
The DTM is a model, not a prediction. Not all countries follow it exactly, and the timescales vary widely.
Exam tip: Be able to place countries at different DTM stages and explain the characteristics of each stage.
Factors influencing birth and death rates
Big idea: Birth and death rates are influenced by a complex mix of social, economic, cultural, and political factors. Understanding these helps explain population differences between countries.
Factors reducing death rates
- Healthcare access: Hospitals, doctors, medicines, vaccinations
- Sanitation: Clean water, sewage treatment, waste disposal
- Nutrition: Food security, diverse diet, reduced malnutrition
- Education: Health awareness, hygiene practices
- Technology: Medical advances, disease treatment
Factors reducing birth rates
- Female education: Strongest single factor — educated women have fewer children later
- Contraception access: Family planning services and information
- Urbanisation: Children become economic cost rather than asset
- Economic development: Social security reduces need for children as old-age support
- Women in workforce: Career opportunities delay/reduce childbearing
- Government policies: Family planning programmes, incentives/disincentives
Female education is the single most effective factor in reducing birth rates. Each additional year of schooling correlates with fewer children.
Exam tip: Link factors to SPECIFIC rates. Healthcare reduces CDR; female education reduces CBR. Dont mix them up!
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IB-style question — Factors affecting population change [2]
In the country of Velara, total fertility rate has fallen from 5.2 to 1.9 over 40 years. Outline two factors that could explain this decline in fertility. [2]
How to answer it, step by step
- Education and status of women
• More girls in education delays marriage/childbirth
• Women in paid work tend to have fewer children - Access and economics
• Better access to contraception/family planning
• Lower infant mortality means fewer 'spare' births needed
Final answer
Examiner tip: 'outline' wants two distinct named factors, each briefly linked to lower fertility — not one factor described twice.
IB-style question — Doubling time from data [1]
Velara's neighbour has an annual population growth rate of 2.8%. Calculate the number of years for its population to double. [1]
How to answer it, step by step
- Rule of 70
• Doubling time = 70 ÷ 2.8
• = 25 years - Interpret
• Population doubles in roughly 25 years
• Indicates rapid (Stage 2) growth
Final answer
Examiner tip: 70 ÷ growth rate gives doubling time directly; round sensibly and include units (years).