1.1 Population dynamics: Describe and suggest reasons for population increase and decrease.

Population and Settlement

Objective 1.1 – Population Dynamics

Population dynamics describe how the size, structure and distribution of a population change over time. Understanding why populations increase or decrease is essential for analysing settlement patterns, resource use and development challenges in the Cambridge IGCSE 0460 syllabus.

1. Key Concepts & Definitions

• Fertility component – measured by the crude birth rate (CBR): number of live births per 1 000 population per year.
• Mortality component – measured by the crude death rate (CDR): number of deaths per 1 000 population per year.
• Migration component – measured by the net migration rate (NMR) or net immigration rate (NIR): (in‑migration – out‑migration) per 1 000 population per year.
• Natural increase = CBR – CDR.
• Natural decrease = CDR – CBR.
• Net migration = in‑migration – out‑migration (positive = net in‑migration, negative = net out‑migration).
• Population momentum – the tendency for a population to continue growing after replacement‑level fertility has been reached, because a large proportion of the population is of child‑bearing age.
• Dependency ratios –
  • Young‑age dependency ratio = (population 0‑14 ÷ population 15‑64) × 100.
  • Old‑age dependency ratio = (population 65+ ÷ population 15‑64) × 100.
  • High ratios indicate greater pressure on the working‑age population.
• Spatial scale – population change can be examined at local, national or global scales; the scale chosen influences the relevance of factors such as migration, policy and data reliability.

2. Causes of Population Increase

• High fertility (high CBR)
  • Cultural or religious preference for large families.
  • Limited access to contraception or family‑planning services.
• Decline in mortality (low CDR)
  • Improved health care, vaccination programmes, nutrition and sanitation.
• Net in‑migration (positive NMR)
  • Better employment, education or safety opportunities attract people.
• Positive natural increase – when CBR > CDR.

3. Causes of Population Decrease

• Low fertility (low CBR)
  • Higher education (especially for women) and career focus.
  • Widespread use of contraception and family‑planning services.
• High mortality (high CDR)
  • Diseases, poor health services, malnutrition or conflict.
• Net out‑migration (negative NMR)
  • Search for better jobs, education or safety (e.g., “brain drain”).
• Negative natural increase – when CDR > CBR.

4. Factors Influencing Birth and Death Rates

• Education (especially of women) – delays marriage, reduces fertility and improves health knowledge, lowering both CBR and CDR.
• Access to contraception & family‑planning – directly reduces CBR; indirect health benefits may lower CDR.
• Economic development – initially raises CBR, later lowers it (demographic transition); consistently reduces CDR through better nutrition and health services.
• Urbanisation – higher living costs and smaller housing units tend to lower CBR; better service provision lowers CDR.
• Conflict or war – may cause a post‑war “baby boom” or suppress fertility; invariably raises CDR.
• Health epidemics (e.g., HIV/AIDS, COVID‑19) – can depress fertility and increase mortality.

5. Demographic Transition Model (DTM)

The DTM links economic development to changes in fertility and mortality, describing four idealised stages.

1. Stage 1 – High stationary: High CBR & CDR → low growth.
2. Stage 2 – Early expanding: CDR falls sharply, CBR remains high → rapid growth.
3. Stage 3 – Late expanding: CBR begins to fall → growth slows.
4. Stage 4 – Low stationary: Low CBR & CDR → population stabilises or declines.

Strengths

• Clear chronological framework linking development to demographic change.
• Useful for predicting future trends in many industrialised nations.

Limitations

• Based on Western European history; may not fit countries with different cultural, religious or policy contexts.
• Ignores the impact of international migration, which can dramatically alter size and structure.
• Assumes a linear, unidirectional path – some societies skip stages or revert (e.g., due to conflict).

Evaluation Framework (AO3)

• Effectiveness – Did the model explain the observed pattern?
• Unintended consequences – E.g., rapid urban growth, environmental pressure.
• Sustainability – Are the implied economic and social trends maintainable?
• Equity – Does the model consider disparities between regions or groups?
• Data reliability – Quality of the statistical evidence supporting each stage.

6. Population Structure: Youthful vs. Ageing

Structure	Typical Age‑Pyramid Shape	Key Implications
Youthful (high % < 25)	Broad base, narrow top	High young‑age dependency, pressure on education & jobs; potential “demographic dividend”.
Ageing (high % > 65)	Narrow base, wide top	Low young‑age dependency, high old‑age dependency; pressure on health care, pensions and social services.

Dependency‑Ratio Example

If a country has 30 % aged 0‑14, 60 % aged 15‑64 and 10 % aged 65+, the young‑age dependency ratio is (30 ÷ 60) × 100 = 50 and the old‑age dependency ratio is (10 ÷ 60) × 100 = 17. These ratios help assess the economic burden on the working‑age population.

7. Population Policies (Pro‑ and Anti‑Natalist)

• Anti‑natalist policies – aim to curb rapid growth.
  • China – One‑Child Policy (1979‑2015) – strict limits, fines, incentives; CBR fell from ~22 to ~12 births/1 000. Unintended effects: gender imbalance, ageing population, “4‑2‑1” family structure.
  • Iran (1990s) – Family‑planning campaign – free contraception, education; CBR dropped from ~25 to ~15 births/1 000 within a decade.
• Pro‑natalist policies – aim to raise low fertility.
  • France – Family allowances, subsidised childcare, generous parental leave – helps maintain one of the highest CBRs in Europe (~12 births/1 000).
  • Singapore – “Baby Bonus” and housing incentives (1980s‑1990s) – modest rise in fertility, but still below replacement level.

Mini‑Case‑Study Evaluation: China’s One‑Child Policy

• Goal – Reduce population growth to alleviate pressure on resources.
• Effectiveness – CBR fell dramatically; total fertility rate dropped below replacement.
• Unintended consequences – Skewed sex ratio (≈ 115 males per 100 females), rapid ageing, “4‑2‑1” caregiving burden.
• Data reliability – Official statistics may under‑report births; independent surveys suggest higher actual fertility.
• Alternative approaches – Voluntary incentives, improved female education, and rural development could have achieved similar fertility decline with fewer side‑effects.

8. International Migration

• Typologies
  • Economic migration – seeking better employment or income.
  • Forced migration – refugees and asylum‑seekers fleeing conflict, persecution or environmental disaster.
  • Seasonal migration – temporary movement for agricultural or tourism work.
• Push‑Pull Factors (example: Rural‑to‑Urban migration in India)
  • Push: Low agricultural wages, limited services, environmental degradation.
  • Pull: Higher urban wages, better education & health facilities, perceived modern lifestyle.
• Impacts
  • Origin areas: Labour loss, possible remittance inflows, ageing rural populations.
  • Destination areas: Rapid urban growth, housing pressure, infrastructure strain, cultural diversification.
• Management Strategies
  • Skilled‑worker visa schemes.
  • Refugee resettlement programmes with integration support.
  • Rural development policies to reduce push factors (e.g., micro‑finance, rural infrastructure).

Case Study – Syrian Refugees (2011‑present)

• Over 5 million displaced; main push factor – armed conflict.
• Pull factor – safety and asylum opportunities in Europe and neighbouring countries.
• Impacts on host nations: pressure on housing, health and education services; but also economic contributions through labour market participation and entrepreneurship.

9. Quantitative Skills

Worked Example – Natural Increase

Country A: CBR = 30 births/1 000, CDR = 12 deaths/1 000, mid‑year population = 10 million.

1. Natural increase = CBR – CDR = 30 – 12 = 18 per 1 000.
2. Annual natural increase = 18/1 000 × 10 000 000 = 180 000 people.

Practice Question – Constructing a Graph

Data for Country B (2015‑2019) are shown below. Draw a simple line graph of CBR over the five years and comment on the trend.

Year	CBR (per 1 000)
2015	28
2016	27
2017	26
2018	25
2019	24

Mini‑Exercise – Identify the DTM Stage

Country	CBR (per 1 000)	CDR (per 1 000)	Likely DTM Stage
Country X	45	40	Stage 1
Country Y	28	10	Stage 2
Country Z	12	8	Stage 3‑4 (transition)

Students should justify their answers by comparing the gap between CBR and CDR.

10. Graphical Skill Tip – Reading a Population Pyramid

• Identify the overall shape (broad base, rectangular, inverted) – indicates youthful, stable or ageing population.
• Width of each age‑group bar shows the proportion of that cohort.
• Bulges or indentations often reflect historic events (e.g., post‑war baby boom, war‑related loss).
• Gender imbalance can signal migration patterns (e.g., male‑dominated labour migration).

11. Data Reliability – Sources & Limitations

• Census – most comprehensive; may miss informal settlements or under‑report births/deaths.
• Sample surveys – quicker, cheaper; subject to sampling error and may overlook rare events.
• Vital‑registration systems – reliable where coverage is complete; many developing nations have incomplete registers.
• Always consider under‑reporting, political bias, and the date of data collection when evaluating statistics.

12. Real‑World Illustrations (2023 UN Data)^†

Population Increase – Nigeria

• CBR ≈ 37 births/1 000; CDR falling due to expanded vaccination and improved nutrition.
• Over 60 % of the population is under 25 – a classic youthful structure with a potential demographic dividend.

Population Decrease – Japan

• CBR ≈ 7 births/1 000; CDR ≈ 11 deaths/1 000 → natural decrease.
• ≈ 28 % of the population is over 65; high old‑age dependency ratio stresses pension and health‑care systems.

^†Data sourced from the United Nations World Population Prospects 2023.

13. Summary Checklist for Exam Answers (AO1‑AO3)

• Define population increase/decrease, natural increase/decrease, and net migration using the correct formulae.
• Identify at least three causes of increase and three causes of decrease (birth rate, death rate, migration).
• Explain how education, contraception, economic development, urbanisation, conflict and epidemics influence CBR and CDR.
• Describe the four DTM stages and evaluate their strengths and limitations using the provided framework.
• Discuss youthful vs ageing population structures, including dependency‑ratio calculations and socio‑economic implications.
• Give examples of pro‑ and anti‑natalist policies; evaluate one policy (e.g., China’s One‑Child Policy) using effectiveness, unintended consequences, sustainability, equity and data reliability.
• Explain push‑pull factors, impacts and management of international migration; include typologies and a brief case‑study (e.g., Syrian refugees).
• Perform a quantitative calculation (e.g., natural increase) and interpret a population pyramid or construct a simple graph from raw data.
• Comment on the reliability of the data used (census, surveys, vital registration) and any limitations.