World Population: Distribution, Density and Growth

Population is the starting point of human geography, because every other pattern, from cropland to city, follows from where people live and how fast their numbers change. The chapter has three parts and examiners ask from all three: distribution, which is how people are spread over the earth; density, which is how many of them there are in a unit of area; and growth, which is how the number changes over time. The vocabulary matters as much as the figures, so learn the definitions precisely. Distribution is a pattern, density is a ratio, and growth is a change.

Distribution of world population

People are spread very unevenly. About nine-tenths of the world's people live in the Northern Hemisphere, and about nine-tenths live on roughly one-tenth of the land surface. Asia alone holds around three-fifths of humanity, which is why it is the most populous continent, followed by Africa, while Oceania is the least populous. Four great clusters account for most of the total: East Asia, South Asia, Western Europe and the north-eastern part of North America. The inhabited part of the earth is called the ecumene and the uninhabited part the non-ecumene; the hot deserts, the equatorial rainforests, the high mountains and the polar lands are nearly empty.

Why people live where they do

The factors are grouped under three heads. Geographical factors come first: availability of fresh water, which is why river valleys such as the Nile, the Ganga and the Hwang Ho are crowded; landforms, because plains are easier to farm and build on than steep slopes; climate, which keeps people out of extreme cold and extreme aridity; and fertile soils, which explain the density of the deltas and the volcanic soils of Java. Economic factors follow: mineral deposits draw settlement, as in the Katanga copper belt and the Chota Nagpur plateau; industrialisation and urbanisation pull people to Osaka, the Ruhr and Mumbai. Social, cultural and political factors complete the list: religious or cultural importance attracts people to places such as Varanasi, while war and political instability empty a region.

Density of population

Density of population is the number of persons per unit area, usually per square kilometre, and it is the simplest measure of the pressure of people on land. Arithmetic density divides the total population by the total area. Physiological density divides it by the arable land alone, and agricultural density divides the farming population by the arable land; both of these are better measures of pressure on cultivable land, and both appear in harder papers. By the Census of 2011 the density of population in India was 382 persons per square kilometre. Among countries, the small city states such as Monaco and Singapore have the highest densities, while Mongolia, Namibia and Greenland are among the most thinly peopled.

Growth of population

Growth may be positive or negative. It is positive when births exceed deaths or when people move in, and negative when deaths exceed births or when people move out, as in parts of eastern Europe. The world took a very long time to reach its first billion, about the year 1804, and then added billions faster and faster as death rates fell with better medicine, sanitation and food supply while birth rates stayed high. The United Nations marked the Day of Eight Billion on 15 November 2022. The rate of growth, however, peaked in the 1960s and has been falling since, so the additions are now slowing. India is the most populous country in the world, having passed China according to United Nations estimates for 2023.

Demographic transition and the Malthusian theory

The theory of demographic transition explains the fall in growth as a country develops. In the first stage, called high stationary, both birth and death rates are high and population grows slowly; society is rural and agrarian. In the second stage, the transitional or early expanding stage, death rates fall sharply because of medicine and sanitation while birth rates remain high, so population grows fast; this is the stage of population explosion. In the third stage, called low stationary, both rates are low, families are small and population is stable or even declines. Thomas Malthus, in An Essay on the Principle of Population published in 1798, argued that population tends to grow in a geometric progression while the means of subsistence grow only in an arithmetic progression, so growth must be checked by what he called positive checks such as famine and disease, or by preventive checks such as late marriage.

Reading a population pyramid

A population pyramid shows the share of each age group by sex. A broad base and a narrow top mean a high birth rate and a young population, as in many African countries; such a pyramid is called expanding. Nearly vertical sides mean birth and death rates are both low and the population is constant, as in Australia. A narrow base means birth rates have fallen below the level of replacement, so the population is declining and ageing, as in Japan. The share of children and old people together gives the dependency ratio, and a large share of working age people is the demographic dividend.