Physiological density measures people against farmland

The definition and the formula

Physiological density divides a country's population by its area of arable land, the land suitable for growing crops. The course framework names it in Topic 2.1 as one of the three methods for calculating population density, alongside arithmetic density, which uses total land area, and agricultural density, which counts only farmers. As a formula it is population divided by arable square kilometres. Because arable land is always smaller than total land, physiological density is always the larger of the two figures for the same country.

What the table shows

The table uses World Bank figures for 2023. Egypt's arithmetic density of about 115 people per square kilometre hides a physiological density of about 3,691, because only about 3.1 percent of its land is arable and, as the article on Egypt notes, the great majority of its people live near the banks of the Nile. Bangladesh has by far the highest arithmetic density, yet its physiological figure sits below Egypt's and Japan's, because about 60 percent of its land can be farmed. Canada's figure rises more than twentyfold between the two measures.

Why the exam cares about the difference

The course framework states the reason in the sentence quoted above: the method chosen reveals different information about the pressure a population exerts on the land. A high physiological density signals that each hectare of farmland must feed many people, which pushes a country toward intensive farming, food imports or both. A low figure, as in Canada or the United States, leaves room for extensive farming. Questions often give two densities for one country and ask what the gap between them implies.

Agricultural density, the measure students confuse with it

Agricultural density divides the number of farmers, not the whole population, by the arable area. It measures how many people work each unit of farmland, so it tends to be high where farming relies on labour and low where it relies on machines. A country can therefore have a high physiological density and a low agricultural density at the same time, when many people depend on farmland worked by relatively few farmers. Mixing up the two numerators, all people against farmers only, is the most common calculation error.

The calculation error that costs the mark

Dividing by total land area and calling the result physiological density is the classic calculation error. Check the denominator. A figure whose denominator includes deserts, mountains and ice is arithmetic density, whatever the question calls it. A second slip is to read a high physiological density as proof of famine. It measures pressure on farmland, not hunger, and trade, technology and yields all change what that pressure means. The strongest answers state the figure, name the denominator, and then explain the consequence for food supply.

Revising density with real numbers

Copy the table above or photograph the density table in your textbook, then practise moving between the three measures, because the exam rewards the calculation and the interpretation together. Photo to quiz builds questions that give a population and an area and ask for the right density, and weak topic analysis shows whether calculation or interpretation is where you lose marks. The Unit 2 page covers the rest of population distribution.

Last updated: 2026-09-27 · Written with AI assistance and reviewed before publishing.