Population Dynamics

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Cambridge (CIE) IGCSE Geography

Population Dynamics

The Big Idea: the world's population is growing fast but unevenly — birth rates, death rates, and migration all pull in different directions in different countries, and every government tries to nudge the balance between people and resources with policy.

Summary 1. Population 2. Population Change 3. Population Policies What to Memorise Checklist Exam Tips

Summary — The Whole Chapter at a Glance

World population is growing by ~80 million people a year, but the growth rate is actually slowing down (2% in 1970 → under 1% in 2022).
Every area has a carrying capacity. Too many people for the resources = overpopulation. Too few people to use the resources = underpopulation. The sweet spot in between is the optimum population.
Population changes in only two ways: natural change (births minus deaths) and migration (immigration minus emigration).
The Demographic Transition Model (DTM) shows 5 stages every country tends to pass through as it develops — birth and death rates start high, fall at different speeds, and eventually settle low (or start to decline).
Fertility and mortality are driven by social, economic, and political factors — not just biology.
Case studies: Nigeria and Niger = rapid growth / overpopulation. Canada = underpopulation. Japan = ageing population / natural decrease.
Governments respond with population policies: anti-natalist (reduce births, e.g. China's one-child policy) or pro-natalist (increase births, e.g. France's family incentives).

1. Population

1.1 The Population Explosion

Here's a fact that should genuinely surprise you: for almost all of human history, the population grew so slowly that it took all of human history up to 1804 just to reach the first billion people. Then something changed. It took only 124 years (1803–1927) to add the second billion. Then 33 years for the third. Then it kept accelerating — by the 1970s and 80s, we were adding a billion people roughly every 12–13 years.

Think of it like a snowball rolling downhill. At the top of the hill it barely moves. But as it picks up momentum, each rotation adds more snow than the last — until, eventually, physics (or in this case, falling birth rates) starts to slow it back down again near the bottom.

TIME TAKEN FOR WORLD POPULATION TO GROW BY 1 BILLION All history → 1 billion : "all of human history up to 1803" 1 → 2 billion : 124 years (1803-1927) 2 → 3 billion : 33 years (1927-1960) 3 → 4 billion : 15 years (1960-1975) 4 → 5 billion : 12 years (1975-1987) 5 → 6 billion : 12 years (1987-1999) 6 → 7 billion : 12 years (1999-2011) 7 → 8 billion : 13 years (2011-2024) 8 → 9 billion : 14 years (2024-2038) [projected] 9 →10 billion : 18 years (2038-2056) [projected] 10→11 billion : 32 years (2056-2088) [projected]

Key distinction — don't mix these up! Population increase is NOT the same as population growth rate. The population can still be increasing even while the growth rate is falling — like a car still moving forward while it's decelerating. The UN predicts population will stabilise at around 11 billion by 2100, with the growth rate approaching 0%.

Practice Question

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Concepts Checklist
Exam Tips & Common Mistakes
1.2 Carrying Capacity, Overpopulation & Underpopulation
2.1 Migration
2.2 Natural Population Change
2.3 The Demographic Transition Model (DTM)
2.4 What Drives Fertility & Mortality? (Social, Economic, Political)
2.5 Case Study: Nigeria — Rapid Growth & Overpopulation

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Population Dynamics