The World Population: Distribution, Density and Growth
It explains why the world's people are spread unevenly across the earth, how that spread is measured by density, and how populations grow and change through births, deaths and migration as captured by the Demographic Transition Theory.
Population geography is a high-yield Prelims zone — sparse vs dense regions, push–pull factors, CBR/CDR definitions and the stages of demographic transition appear as direct MCQs. In Mains GS-I it anchors the 'population and associated issues' and 'factors responsible for the location of industries and the distribution of population' themes, and feeds society topics like migration and urbanisation. The Malthusian angle also connects to GS-III sustainability and resource debates.
Understand the chapter
Uneven Distribution of World Population
Population distribution is the way people are spaced over the earth's surface, and it is strikingly uneven — roughly 90% of humanity lives on only about 10% of the land. The 10 most populous countries together hold nearly 60% of the world total, and 6 of these lie in Asia. Cressey summed up Asia, and the world, as having many places where people are few and few places where people are very many.
- World population crossed 6 billion at the start of the 21st century.
- 90% of people live on ~10% of land area.
- Top 10 populous countries = ~60% of world; 6 are in Asia.
- Distribution = spacing of people; density = people per unit area.
Density of Population
Each unit of land has a limited capacity to support people, so density of population measures the ratio of people to land, expressed in persons per sq km. It is calculated as population divided by area. For example, 1,50,000 persons over 100 sq km gives a density of 1,500 persons/sq km, signalling heavy demographic pressure on that land.
- Density of Population = Population ÷ Area (persons/sq km).
- Worked example: 1,50,000 ÷ 100 = 1,500 persons/sq km.
- Density reveals the man–land pressure of a region.
Factors Influencing Distribution
Three sets of factors explain where people cluster. Geographical factors set the natural stage, economic factors pull workers toward opportunity, and social, cultural and political factors attract or repel people. River valleys and fertile plains are crowded, while hot and cold deserts, dense equatorial forests, high mountains and polar areas stay sparse.
- Geographical: availability of water, landforms (flat plains), climate, fertile soils.
- Economic: minerals (Katanga–Zambia copper belt), urbanisation, industrialisation (Kobe–Osaka, Japan).
- Social/cultural: religious–cultural pull; unrest pushes people out; govt incentives redistribute.
- Dense: Ganga plains; sparse: Himalayas, deserts, equatorial forests.
Population Growth and Its Components
Population change is the change in inhabitants of a territory over a period, positive or negative, shown in absolute numbers or as a percentage. Natural growth counts only births minus deaths, whereas actual growth also adds in-migration and subtracts out-migration. The three components of change are births, deaths and migration, with births and deaths measured by CBR and CDR per thousand of mid-year population.
- Growth of population = absolute change; growth rate = the same change in percentage.
- Natural Growth = Births − Deaths.
- Actual Growth = Births − Deaths + In-migration − Out-migration.
- CBR = (B/P)×1000; CDR = (D/P)×1000, where P = mid-year population.
Migration: Push and Pull
Migration is the third component, moving people from a place of origin (which loses population) to a place of destination (which gains). The same person is an emigrant at origin and an immigrant at destination. It may be permanent, temporary or seasonal and flow between rural and urban areas in any direction, driven by push factors at origin and pull factors at destination.
- Immigrant moves in; emigrant moves out — one person can be both.
- Push (origin): unemployment, poor living conditions, unrest, disasters, epidemics.
- Pull (destination): better jobs, living conditions, peace, security, pleasant climate.
- Migration = a spontaneous effort to balance population with resources.
Demographic Transition Theory
The Demographic Transition Theory describes and predicts how a society's population shifts from high births–high deaths to low births–low deaths as it moves from rural, agrarian and illiterate to urban, industrial and literate. These changes occur in three stages collectively called the demographic cycle. The widest gap between birth and death rates — and hence the fastest growth — comes in the second stage, when deaths fall but births stay high.
- Stage 1: high CBR + high CDR, slow growth, agrarian/illiterate (e.g., rainforest tribes); all nations were here 200 years ago.
- Stage 2: CBR stays high while CDR falls (sanitation/health) → high net addition (e.g., Bangladesh, Sri Lanka, Kenya).
- Stage 3: low CBR + low CDR, stable/slow growth, urban-literate, family size controlled (e.g., Canada, Japan, USA).
- Different countries sit at different stages today.
Population Control and Malthus
Family planning — the spacing or preventing of births — is central to limiting growth and improving women's health, supported by propaganda, free contraceptives and tax disincentives for large families. Thomas Malthus (1798) warned that population grows faster than food supply, so unchecked growth ends in a crash through famine, disease and war. He judged preventive checks superior, and sustainability of resources demands controlling rapid population increase.
- Family planning = spacing/preventing births; improves women's health.
- Measures: propaganda, free contraceptives, tax disincentives for large families.
- Malthus (1798): population outpaces food → famine, disease, war.
- Preventive checks preferred over positive checks.
Key terms
- Population distribution
- The way people are spaced over the earth's surface; broadly very uneven.
- Density of population
- Ratio of people to land area, in persons per sq km (Population ÷ Area).
- Crude Birth Rate (CBR)
- Live births in a year per 1,000 of mid-year population: (B/P)×1000.
- Crude Death Rate (CDR)
- Deaths in a year per 1,000 of mid-year population: (D/P)×1000.
- Natural growth
- Population added by births minus deaths only, excluding migration.
- Actual growth
- Births − Deaths + In-migration − Out-migration.
- Immigrant vs Emigrant
- Immigrant moves into a place; emigrant moves out — the same person can be both.
- Push and pull factors
- Push repels at origin (unemployment, disasters); pull attracts at destination (jobs, peace).
- Demographic cycle
- The set of stages through which births and deaths fall as a society modernises.
- Family planning
- Spacing or preventing births to limit growth and improve women's health.
Must-know facts exam-ready
- World population crossed 6 billion at the beginning of the 21st century.
- About 90% of the world's people live on only ~10% of its land area.
- The 10 most populous countries hold ~60% of world population; 6 of them are in Asia.
- Density of Population = Population ÷ Area, measured in persons per sq km.
- CBR = (live births ÷ mid-year population)×1000; CDR = (deaths ÷ mid-year population)×1000.
- Natural Growth = Births − Deaths; Actual Growth = Births − Deaths + In-migration − Out-migration.
- India: 2001 population 102.70 crore, 2011 population 121.02 crore — a growth of 18.15 crore (Census of India).
- Three components of population change: births, deaths and migration.
- Human population rose more than 10 times in the last 500 years and 4 times in the 20th century.
- Africa records the highest rate of population growth among continents.
- Thomas Malthus (1798): population grows faster than food supply, risking a crash via famine, disease and war.
- Examples: Katanga–Zambia copper belt (minerals) and Kobe–Osaka, Japan (industry) draw dense population; Ganga plains are among the most densely populated.
Memory tricks remember it for good
Traps to avoid
- Natural growth excludes migration; actual growth includes in- and out-migration — don't equate them.
- Growth of population is the absolute change; growth RATE is that change expressed as a percentage.
- Positive growth can come from in-migration (not only births>deaths); negative growth can come from out-migration (not only deaths>births).
- Medical and educational facilities are PULL factors, not push factors — a classic exam trap.
- South-east Asia is densely populated; the Atacama, the equatorial region and polar areas are the sparse ones.
- Stage 1 of demographic transition has SLOW growth despite high birth rate, because the death rate is equally high — high births ≠ high growth.
Exam focus
🧠 Prelims angles
- Classifying sparse vs dense regions: Atacama/equatorial/polar (sparse) vs SE Asia and Ganga plains (dense).
- Push vs pull factor identification, including the medical/educational = pull trap.
- Definitions and formulae of CBR and CDR (per 1,000 of mid-year population).
- Demographic transition stages with world examples (rainforest tribes; Bangladesh/Sri Lanka/Kenya; Canada/Japan/USA).
- Continent with the highest population growth = Africa; 6 of the top-10 populous countries are in Asia.
- Malthus theory year (1798), its core idea, and preventive vs positive checks.
✍️ Mains angles GS-I
- Discuss the geographical, economic and socio-cultural factors influencing the distribution and density of world population.Structure by the three heads with one concrete example each (Ganga plains, Katanga copper belt, Kobe–Osaka).
- Explain the three stages of the Demographic Transition Theory and locate countries within them.Track CBR–CDR behaviour per stage, flag Stage 2 as the fast-growth gap phase, and link to socio-economic development.
- Critically examine the Malthusian view in light of modern food production and family planning.Contrast preventive vs positive checks and bring in sustainability and population-control measures.
- Migration is a spontaneous effort to balance population and resources — analyse using push–pull dynamics.Use rural-to-urban migration and origin/destination effects to argue both costs and benefits.
Last-minute revision tick as you recall
- 90% of people on ~10% of land; distribution is uneven (Cressey).
- Top 10 populous = ~60% of world; 6 in Asia; world crossed 6 billion in the 21st c.
- Density = Population ÷ Area (persons/sq km).
- Distribution factors: Geographical (WLCS), Economic (MUI), Social-cultural.
- Components of change: Births, Deaths, Migration (BDM).
- CBR = B/P×1000; CDR = D/P×1000 (mid-year P).
- Natural = B − D; Actual = B − D + In − Out migration.
- Push = problems at origin; Pull = perks at destination.
- Demographic transition HH→HL→LL, Stage 2 grows fastest; Malthus 1798; Africa has the highest growth.
Distilled from NCERT Class 12 · Fundamentals of Human Geography for UPSC. Always cross-check facts with the original NCERT.