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Geography Quiz

Population Distribution and Density

Population distribution describes where people live across the surface of the Earth, and population density measures how tightly they are packed into a given area. These notes cover the difference between distribution and density, the three measures of density used in geography, the physical and human factors that produce dense and sparse regions, the world pattern of population concentration, the demographic transition model, migration and the push and pull framework, population structure read from age-sex pyramids, and the consequences of overpopulation and underpopulation. A 20-question practice set follows.

Distribution, Density and How They Are Measured

Distribution and density are related but distinct. Distribution is a pattern, describing the arrangement of people over space, and is best shown by a dot map. Density is a ratio, describing the number of people per unit area, and is best shown by a choropleth map with shaded classes.

  • Population distribution: the way people are spread over an area; described as dense, sparse, clustered, linear, random or uniform.
  • Arithmetic (crude) density equals total population divided by total land area, expressed as persons per square kilometre. It is the simplest measure but hides internal variation.
  • Physiological density equals total population divided by the area of arable land. It is a better indicator of pressure on food-producing land, and is very high in countries such as Egypt where most land is desert.
  • Agricultural density equals the farming population divided by the area of arable land. A high agricultural density with low output usually indicates subsistence farming and low mechanisation.
  • World average population density is roughly 60 persons per square kilometre of land area, but the range is enormous, from under 3 in Mongolia, Namibia and Australia to several thousand in Bangladesh, Singapore and the small island and city states.
  • About 90 percent of the world's people live in the Northern Hemisphere, and roughly 90 percent live on about 10 percent of the land surface.
  • Population is measured by a census, normally taken every ten years, supplemented by vital registration of births and deaths and by sample surveys.

Factors Affecting Distribution

Physical factors set the broad limits of where settlement is possible, and human factors decide where within those limits people actually concentrate. Increasingly it is economic and political factors, rather than physical ones, that explain the very densest clusters.

  • Relief: lowland plains and river valleys attract dense settlement because they are easy to build on, farm and cross; steep, rugged mountains such as the Himalayas and the Andes repel it.
  • Climate: temperate and equable climates with reliable rainfall attract population; extremes repel it, including hot deserts such as the Sahara, cold polar regions such as northern Siberia and Greenland, and very wet equatorial rainforest such as the Amazon and Congo basins.
  • Soils: deep, fertile alluvial and volcanic soils support intensive agriculture and dense rural population, as in the Ganges, Nile, Yangtze and Indus valleys and on the volcanic soils of Java.
  • Water supply: settlement follows fresh water, which is why the Nile valley concentrates almost the entire population of Egypt on a narrow strip.
  • Mineral and energy resources: mining and oil have created dense settlement in otherwise hostile environments, for example the Witwatersrand goldfields of South Africa and the Persian Gulf oil states.
  • Economic factors: industry, ports, trade and services concentrate people in cities. The largest clusters today are urban and industrial, not agricultural.
  • Transport and accessibility: coastlines, navigable rivers, railways and major roads create linear zones of dense settlement; some 40 percent of the world's population lives within about 100 kilometres of a coast.
  • Social, political and historical factors: government policy, planned capitals, land tenure, security, conflict and colonial settlement patterns all redistribute population. War and persecution can rapidly depopulate an area.

World Pattern, Migration and Change Over Time

Four great clusters account for most of humanity: East Asia, South Asia, Europe, and the north-eastern United States with south-eastern Canada. The pattern is not static, because population changes through natural increase, which is births minus deaths, and through net migration.

  • Densely populated regions: East Asia (eastern China, Japan, the Korean peninsula), South Asia (India, Bangladesh, Pakistan, Sri Lanka), Western and Central Europe, north-east United States, the Nile valley and the Java lowlands.
  • Sparsely populated regions: the Sahara and Kalahari deserts, the Arabian interior, Amazonia and the Congo basin, the Himalayas and the Andes, Siberia, northern Canada, Greenland, Antarctica and the Australian interior.
  • Natural increase rate equals crude birth rate minus crude death rate, usually expressed per 1000 people or as a percentage. Growth rate adds net migration to natural increase.
  • Doubling time can be estimated by dividing 70 by the annual percentage growth rate.
  • The demographic transition model has four widely used stages, with a fifth often added. Stage one: high fluctuating birth and death rates, low growth. Stage two: death rate falls sharply with better food, sanitation and medicine while the birth rate stays high, so growth is rapid. Stage three: the birth rate falls with urbanisation, education of women and contraception, so growth slows. Stage four: both rates low, population stable. Stage five: birth rate below death rate, population declining and ageing, as in Japan, Italy and Germany.
  • Migration is classified as internal or international, and as voluntary or forced. Rural to urban migration is the dominant internal flow in developing countries and is the main driver of rapid urbanisation.
  • Push factors drive people away: unemployment, poverty, drought, famine, war, persecution, natural disaster and lack of services. Pull factors attract them: jobs, higher wages, education, healthcare, safety and family links.
  • Ravenstein's laws of migration state, among other things, that most migrants travel short distances, that migration proceeds in steps, that every migration stream produces a counter-stream, and that urban dwellers are less migratory than rural ones.

Population Structure and Its Consequences

Population structure is the composition of a population by age and sex, displayed as a population pyramid. The shape of the pyramid summarises a country's demographic stage and predicts the pressures it will face, and this makes pyramid interpretation a favourite examination task.

  • A broad-based, steeply tapering pyramid indicates high birth and death rates, a young population and a high youth dependency, typical of stage two countries such as Niger and Uganda.
  • A narrow-based, barrel or urn-shaped pyramid indicates low birth rates and long life expectancy, an ageing population and a high elderly dependency, typical of stage four and five countries such as Japan and Germany.
  • The dependency ratio compares the population aged under 15 and over 64 with the working-age population aged 15 to 64, multiplied by 100. A high ratio means fewer workers supporting more dependents.
  • The sex ratio is normally expressed as the number of males per 100 females, or in India as the number of females per 1000 males. Imbalances arise from war, sex-selective practices and labour migration, which is why several Gulf states have far more men than women.
  • Overpopulation exists where population exceeds the resources and technology available to maintain a reasonable standard of living, producing unemployment, food and water shortage, pressure on housing, health and schooling, slum growth and environmental degradation.
  • Underpopulation exists where there are too few people to use the resources of an area fully, as in parts of Canada and Australia; it can mean labour shortage and underused infrastructure.
  • Optimum population is the number of people that, with the available resources and technology, produces the highest quality of life or output per person.
  • Thomas Malthus argued in 1798 that population grows geometrically while food supply grows arithmetically, so that population would be checked by famine, disease and war. Ester Boserup argued the reverse, that population pressure stimulates agricultural innovation, summarised as necessity being the mother of invention.
  • Policy responses include anti-natalist policies to reduce births, such as China's former one-child policy, and pro-natalist policies to raise births through incentives, as in France, Sweden and Japan.

Key Terms

Physiological density
Total population divided by the area of arable land; a better measure of pressure on food-producing land than arithmetic density.
Natural increase rate
Crude birth rate minus crude death rate, showing population change before migration is taken into account.
Demographic transition model
A model describing the shift from high birth and death rates to low ones as a country develops, usually presented in four or five stages.
Dependency ratio
The number of people under 15 and over 64 for every 100 people of working age, indicating the economic burden on the productive population.

Practice Quiz — 20 Questions

correct out of 20

  1. Population density is best defined as:

    • A.The pattern of settlement across a region
    • B.The number of people per unit area
    • C.The rate of population growth
    • D.The total population of a country
    B. The number of people per unit area — Density is a ratio of people to area, whereas distribution describes the spatial pattern.

  2. Which map type is most suitable for showing population distribution?

    • A.Choropleth map
    • B.Dot map
    • C.Isopleth map
    • D.Flow-line map
    B. Dot map — A dot map places one dot for a fixed number of people and shows exactly where the population is located.

  3. Physiological density is calculated as population divided by:

    • A.Total land area
    • B.Arable land area
    • C.Urban area
    • D.Forest area
    B. Arable land area — Using only cultivable land shows the true pressure on food-producing resources.

  4. A country with a large desert area will have an arithmetic density that is:

    • A.Higher than its physiological density
    • B.Much lower than its physiological density
    • C.Identical to its physiological density
    • D.Impossible to calculate
    B. Much lower than its physiological density — Dividing by all land, including uninhabitable desert, makes arithmetic density look low compared with the very high physiological density on the small arable strip.

  5. Approximately what share of the world's population lives in the Northern Hemisphere?

    • A.50 percent
    • B.70 percent
    • C.90 percent
    • D.100 percent
    C. 90 percent — About nine tenths of humanity lives north of the equator, where most of the land area lies.

  6. Which of the following is a physical factor affecting population distribution?

    • A.Government policy
    • B.Relief and soils
    • C.Industrial development
    • D.Transport networks
    B. Relief and soils — Relief, climate, soils and water supply are physical factors; the others are human factors.

  7. The population of Egypt is concentrated along the Nile mainly because of:

    • A.Mineral wealth
    • B.Water supply and fertile alluvial soil
    • C.Cool climate
    • D.Mountain protection
    B. Water supply and fertile alluvial soil — The river provides the only reliable water and the silt-enriched land in an otherwise arid country.

  8. Which of these areas is sparsely populated because of extreme cold?

    • A.Java
    • B.Northern Siberia
    • C.The Ganges plain
    • D.Western Europe
    B. Northern Siberia — Long severe winters, permafrost and a short growing season make northern Siberia very thinly settled.

  9. Dense population on the island of Java is chiefly explained by:

    • A.Oil reserves
    • B.Fertile volcanic soils
    • C.A cold climate
    • D.Glacial deposits
    B. Fertile volcanic soils — Weathered volcanic ash produces exceptionally fertile soil supporting intensive rice cultivation.

  10. Natural increase rate is calculated as:

    • A.Birth rate plus death rate
    • B.Birth rate minus death rate
    • C.Birth rate minus migration
    • D.Death rate minus migration
    B. Birth rate minus death rate — Natural increase excludes migration and measures change from births and deaths alone.

  11. If a population grows at 2 percent per year, its approximate doubling time is:

    • A.14 years
    • B.35 years
    • C.50 years
    • D.70 years
    B. 35 years — Dividing 70 by the growth rate gives 70 divided by 2, which is 35 years.

  12. In stage two of the demographic transition model:

    • A.Both birth and death rates are high
    • B.The death rate falls while the birth rate stays high
    • C.Both rates are low
    • D.The birth rate falls below the death rate
    B. The death rate falls while the birth rate stays high — Improved food supply, sanitation and medicine cut the death rate first, producing rapid population growth.

  13. A country in stage five of the demographic transition model will typically show:

    • A.Rapid growth and a young population
    • B.A declining, ageing population
    • C.High birth and high death rates
    • D.A stable population with high fertility
    B. A declining, ageing population — When the birth rate falls below the death rate the population shrinks and the median age rises.

  14. Which of the following is a push factor for migration?

    • A.Better job opportunities
    • B.Higher wages
    • C.Drought and famine
    • D.Good schools
    C. Drought and famine — Push factors are negative conditions in the source area that drive people to leave.

  15. A population pyramid with a very wide base and narrow top indicates:

    • A.Low birth rate and ageing population
    • B.High birth rate and high youth dependency
    • C.Balanced structure
    • D.Net immigration of elderly people
    B. High birth rate and high youth dependency — A broad base means many children, characteristic of a high fertility, rapidly growing population.

  16. The dependency ratio compares the non-working age groups with people aged:

    • A.0 to 14
    • B.15 to 64
    • C.18 to 60
    • D.65 and over
    B. 15 to 64 — The working age band of 15 to 64 forms the denominator of the ratio.

  17. Rural to urban migration in developing countries most directly causes:

    • A.Rapid urbanisation and slum growth
    • B.Rural overcrowding
    • C.Falling city populations
    • D.Decline in the dependency ratio
    A. Rapid urbanisation and slum growth — Large inflows outpace housing and services, producing informal settlements on the urban fringe.

  18. Thomas Malthus argued that:

    • A.Population pressure stimulates innovation
    • B.Food supply grows geometrically
    • C.Population grows geometrically while food supply grows arithmetically
    • D.Population always matches resources
    C. Population grows geometrically while food supply grows arithmetically — Malthus predicted that unchecked population growth would outrun food production and be limited by famine, disease and war.

  19. Ester Boserup's view of population growth was that:

    • A.It inevitably causes famine
    • B.It stimulates agricultural innovation and higher yields
    • C.It has no effect on food production
    • D.It reduces the labour force
    B. It stimulates agricultural innovation and higher yields — Boserup argued that rising population pressure forces intensification and technological change in farming.

  20. An area with too few people to develop its resources fully is described as:

    • A.Overpopulated
    • B.Underpopulated
    • C.At optimum population
    • D.Densely populated
    B. Underpopulated — Underpopulation means labour and skills are insufficient to exploit the available resources, as in parts of Canada and Australia.

References