Distribution and density
Distribution means the pattern of where people live. Density means how crowded a place is.
Density = number of people ÷ area (usually people per sq km).
About 90% of the world's people live on only about 10% of its land. Crowded areas: river plains of South and East Asia, north-west Europe, the east of North America. Empty areas: hot deserts, polar lands, thick equatorial forests and high mountains.
Factors that affect distribution
1. Geographical factors
- Water: people settle near rivers and lakes for drinking, farming and transport.
- Landform: flat plains and gentle slopes are easy for farms, roads and houses.
- Climate: very hot, very cold or very wet places are hard to live in.
- Soil: fertile soil feeds many people.
2. Economic factors
- Minerals: mining areas attract workers.
- Urbanisation: cities offer jobs, schools and hospitals.
- Industrialisation: factories give jobs and draw many people.
3. Social and cultural factors
Holy places, peaceful areas and good government plans attract people. War, unrest or discrimination make them leave.
Growth of world population
Population growth = change in the number of people between two times. It can be shown as a number or as a percent (growth rate). Positive growth: births more than deaths. Negative growth: numbers fall.
The world had well under 1 billion people for most of history. It reached about 1 billion around 1800, 2 billion by the late 1920s, and then added each new billion faster and faster, reaching about 8 billion in 2022. The time needed to double the population became much shorter. Reasons: better farming (more food), the industrial revolution, better medicine and clean water that cut deaths.
Components of population change
- Births: crude birth rate (CBR) = live births in a year per 1000 people.
- Deaths: crude death rate (CDR) = deaths in a year per 1000 people.
- Migration: moving from one place to another. The place left is the place of origin; the place reached is the place of destination. Immigration = coming in; emigration = going out.
Push and pull factors
Push factors make people leave: unemployment, poor living conditions, unrest, natural disasters, epidemics. Pull factors make people come: jobs, better pay, peace, good schools and hospitals, pleasant climate.
Demographic transition theory
This theory explains how the population of a place changes as it moves from a rural, farming, less literate society to an urban, industrial, literate one.
- Stage 1: high birth rate and high death rate (disease, famine). Growth is slow. Most people are farmers.
- Stage 2: birth rate stays high but death rate falls (better health and food). Population grows very fast.
- Stage 3: both birth and death rates are low. Families are small; people live in cities and are educated. Population becomes steady.
Many rich countries are in stage 3; many poorer countries are still moving through stage 2.
Population control
When growth is too fast, food, water, jobs and schools fall short. Countries try to slow it by:
- Family planning: spacing and limiting births; easy access to contraceptives.
- Education, especially for girls, and a later age of marriage.
- Health care so that fewer children die, and families feel safe having fewer.
- Incentives and awareness campaigns.
A thinker, Thomas Malthus, warned long ago that population could grow faster than food supply. Today the aim is balance, not only fewer people.
Key formulas and definitions
- Density = population ÷ area (people per sq km)
- Growth rate (natural) = CBR − CDR (per 1000); divide by 10 for %
- Total change = births − deaths + in-migrants − out-migrants
- CBR = births per 1000 people per year; CDR = deaths per 1000 people per year
- Push factors = reasons to leave; pull factors = reasons to come
- Demographic transition: Stage 1 high/high → Stage 2 high/low → Stage 3 low/low
Worked examples
1. A town has 50,000 people on 25 sq km. Find its density.
Density = 50,000 ÷ 25 = 2,000 people per sq km.
2. A country has CBR 24 and CDR 8. Find its natural growth rate.
24 − 8 = 16 per 1000 = 1.6% per year.
3. A city of 10,00,000 people has 20,000 births, 7,000 deaths, 15,000 people coming in and 3,000 leaving in a year. What is the total change?
20,000 − 7,000 + 15,000 − 3,000 = 25,000 more people.
4. A region has 20 lakh people on 500 sq km. Another has 20 lakh on 40,000 sq km. Which is denser and why might it be?
First: 4,000 per sq km; second: 50 per sq km. The first is likely a fertile plain or city; the second may be a desert or mountain area.
5. In a country the death rate fell from 25 to 10 but the birth rate stayed at 40. Which stage is it in and what happens?
Stage 2 of demographic transition. Growth rises from 15 to 30 per 1000: a population boom.
6. A country has CBR 9 and CDR 11. What does this show?
Growth = −2 per 1000: negative growth; the population is shrinking (unless migrants come in).
Common mistakes
- Confusing distribution with density. Distribution is the pattern (where); density is the number per sq km (how crowded).
- Forgetting migration when finding total change. Natural growth uses only births and deaths.
- Thinking stage 2 has high deaths. In stage 2 deaths fall, births stay high, so growth is fastest.
- Using percent and per-1000 the same way. 16 per 1000 is 1.6%, not 16%.