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Wyatt's Notes — IB

Population Distribution

Population Distribution

This section covers the IB Geography core extension on population distribution — changing population. It examines the factors that influence where people live, the dynamics of population change, the models used to explain demographic transition, patterns and causes of migration, and the policies governments use to influence population trends. Population geography is central to the IB course and connects closely to themes of development, resource management, and urbanisation.

Contents

Key Concepts

  • Demographic Transition Model (DTM) — a five-stage model describing how population growth changes as a country develops economically, from high birth and death rates (Stage 1) to low birth and death rates (Stage 5). Useful as a general framework but criticised for being Eurocentric and oversimplifying diverse national experiences.
  • Population pyramids — graphical representations of a country”s age-sex structure. The shape of a pyramid reveals information about birth rates, death rates, life expectancy, and migration patterns. Expanding pyramids indicate high growth; contracting pyramids indicate decline.
  • Push and pull factors — Lee’s (1966) migration model explains migration as a result of push factors that drive people away from their origin (e.g., conflict, unemployment, natural disasters) and pull factors that attract them to a destination (e.g., job opportunities, safety, family reunification).
  • Population policies — government measures designed to influence fertility, mortality, or migration. Examples include China’s one-child policy (anti-natalist) and Singapore’s “Have Three or More” campaign (pro-natalist). Their effectiveness depends on enforcement, cultural context, and economic incentives.
  • Dependency ratio — the ratio of economically dependent people (young and old) to the working-age population. A high youth dependency ratio strains education and healthcare systems, while a high old-age dependency ratio strains pension and healthcare systems.
  • Malthus vs. Boserup — Malthus argued that population growth would outstrip food supply, leading to inevitable checks (famine, disease). Boserup countered that population pressure drives agricultural innovation, so food production adapts to meet demand.
  • Demographic dividend — a period when the proportion of the working-age population (15-64) is large relative to dependents (under 15 and over 64). If accompanied by economic growth, education investment, and job creation, the demographic dividend accelerates development (East Asian Tigers in the 1960s-1980s). Without these conditions, it becomes a demographic burden (youth unemployment in sub-Saharan Africa).
  • Forced migration and environmental refugees — people displaced by environmental factors (sea-level rise, desertification, extreme weather) who cross international borders. This category is not formally recognised in the 1951 Refugee Convention, creating legal and humanitarian gaps that are increasingly relevant as climate change intensifies displacement.
  • Population momentum — the continued growth of a population even after fertility rates have fallen to replacement level (approximately 2.1 children per woman), caused by the large number of women of childbearing age in a youthful population structure. India and Nigeria illustrate this: even as TFR declines, absolute population continues to grow for decades.
  • Ageing population — a population structure characterised by a high proportion of elderly people (in most cases 65+), resulting from low fertility rates and increasing life expectancy. Japan, Germany, and Italy face challenges including labour shortages, increased healthcare and pension costs, and the need for immigration to sustain economic output.

Exam Focus

Paper 2 questions on population in most cases require:

  • Describing and explaining population distribution patterns at a global or regional scale.
  • Evaluating the applicability of the DTM to a specific country using demographic data.
  • Analysing the causes and consequences of migration using case studies from contrasting contexts.
  • Assessing the effectiveness of population policies with reference to specific country examples.
  • Interpreting population pyramids, demographic data, and projections.
  • Discussing the concept of population momentum and explaining why populations continue to grow after fertility falls to replacement level, using specific country examples.
  • Evaluating the demographic dividend as both an opportunity and a potential burden, contrasting East Asian Tigers with contemporary sub-Saharan African nations.
  • Analysing the causes and consequences of forced and environmental migration, linking population dynamics to climate change and resource scarcity in extended responses.
  • Interpreting UN World Population Prospects data, including understanding projection uncertainty ranges and the assumptions underlying different variant scenarios (low, medium, high).

Worked Examples

Example 1: Analysing a Population Pyramid

Problem: A country has a population pyramid with a wide base (large proportion aged 0-14), narrow top, and rapidly tapering sides above age 60. At what stage of the DTM is this country, and what are the implications? Solution: The wide base indicates high birth rates; the narrow top indicates high death rates and low life expectancy. This is characteristic of Stage 2 of the DTM. Implications: a high youth dependency ratio strains education and healthcare systems; a rapidly growing working-age population in the future could provide a demographic dividend if accompanied by economic growth and job creation (e.g., sub-Saharan African countries like Niger).

Example 2: Evaluating Anti-Natalist Policy

Problem: Evaluate the effectiveness of China’s one-child policy (1979-2015). Solution: The policy significantly reduced China’s total fertility rate (from approximately 5.8 to 1.6) and is estimated to have prevented 400 million births, easing pressure on resources and accelerating economic development. However, it caused significant social problems: gender imbalance due to selective abortion favouring males (estimated 30 million “surplus” men), an ageing population with a shrinking workforce, and enforcement abuses (forced abortions, fines). The policy’s effectiveness in reducing population growth is clear, but its social costs and ethical issues must be weighed.

Common Pitfalls

  • Treating the DTM as universal: The model is based on the Western European experience. Countries like China (government intervention) and some oil-rich Gulf states (high GDP despite high birth rates) do not fit neatly into the five stages.
  • Confusing push and pull factors: Push factors originate at the source (e.g., conflict, unemployment); pull factors attract to the destination (e.g., job opportunities, safety). Do not reverse them.
  • Ignoring intervening obstacles: Lee’s migration model includes intervening obstacles (distance, cost, border policies) between origin and destination. These should be discussed in migration answers.

Cross-Topic Connections

Population dynamics do not exist in isolation. The study of population distribution connects directly to several other areas of the IB Geography syllabus and is a frequent source of synoptic questions on Paper 2 and Paper 3.

  • Freshwater issues: Rapid population growth in arid regions exacerbates physical water scarcity. Sub-Saharan Africa illustrates this evidently: countries with Stage 2 demographics face both high population growth and limited freshwater access, creating a compound crisis. The Colorado River basin demonstrates how population pressure (Las Vegas, Phoenix) intensifies demand on an already over-allocated river system, where allocation agreements made in the 1920s could not anticipate current demand levels.

  • Urban environments: Rural-urban migration drives urbanisation in developing countries. The demographic transition from Stage 2 to Stage 3 is closely linked to the movement of people from rural to urban areas, as industrialisation creates pull factors in cities. Megacities in South and Southeast Asia (Delhi, Dhaka, Manila) are direct products of population dynamics interacting with urbanisation. Exam questions may ask students to explain how migration affects both the origin and destination areas simultaneously.

  • Climate change: Population distribution is being reshaped by climate impacts in ways that traditional models do not fully capture. Environmental migration is increasingly significant: rising sea levels threaten low-lying populations in Bangladesh and Pacific Island nations; desertification pushes pastoral communities in the Sahel toward urban areas; increased storm frequency displaces coastal populations in the Caribbean. These flows are not captured by Lee’s model but are assessable in Paper 3 extended responses and are relevant to the Extended Essay.

  • Economic development: The demographic dividend — a period when the working-age population is large relative to dependents — is a key driver of economic growth in transitioning economies. The East Asian Tigers (South Korea, Taiwan, Singapore) exploited this window in the late twentieth century; sub-Saharan African countries are approaching it now. Conversely, ageing populations in Japan and Western Europe create labour shortages and increased dependency costs that constrain fiscal policy and require immigration to sustain economic output.

  • Geographic skills: Population data (pyramids, cohort data, migration statistics) provide rich material for Paper 3 geographic skills questions. Students should practise constructing and interpreting age-sex pyramids from census data, calculating dependency ratios, and evaluating the reliability of demographic projections — particularly the uncertainty ranges that accompany UN World Population Prospects data.

Summary

Population distribution covers the Demographic Transition Model, population pyramids, migration theories (Lee’s model, push-pull factors), population policies (pro-natalist and anti-natalist), and the Malthus-Boserup debate. Students must analyse demographic data, evaluate population policies with case study evidence, and understand how population dynamics interact with development and resource management.