The big idea: A megacity is a city with 10 million or more inhabitants.
The number of megacities has grown fast — most new ones are in Asia and Africa, where cities are growing very quickly. Rapid growth brings both problems and benefits.
Key terms
- Megacity — an urban area with a population of 10 million or more.
- Rapid urban growth — a city's population rising quickly, from migration and natural increase.
- Urbanisation — the rising share of people who live in towns and cities.
- Informal settlement — unplanned, often self-built housing (a slum) that grows when a city expands faster than it can house people.
Where megacities are: Most of today's megacities are in lower- and middle-income countries.
By 2030 the countries forecast to hold the most megacities are China and India — both have huge, fast-growing urban populations.
Rapid megacity growth has two sides. A good answer can give drawbacks and benefits, and say who feels each — an individual (one resident) or wider society (the whole city or country).
| Drawbacks (problems) | Benefits (opportunities) |
|---|---|
| Housing shortages and informal settlements (slums) | More jobs and higher wages than in rural areas |
| Traffic congestion and air pollution | Better access to schools, hospitals and services |
| Pressure on water, sanitation and electricity | Economic growth — megacities drive national GDP |
| Unemployment and inequality | Easier to provide services to people who are close together |
How this is tested: Paper 2 Q1/Q5 asks you to Explain two downsides of fast growth, or two benefits — usually [4 marks], 2 per developed point.
Stop wasting time on topics you know
Our AI identifies your weak areas and focuses your study time where it matters. No more overstudying easy topics.
Try Smart Study Free7-day free trial • No card required
Two scales of benefit: Megacity growth can help individuals (one person) and wider society (the whole city or country):
- An individual gains a job, higher pay or access to a hospital or university. - Society gains because megacities create wealth, drive national GDP and make services cheaper to provide to people living close together.
Ways an individual benefits
- Better-paid work — far more, and higher-paid, jobs than in the countryside.
- Services nearby — schools, hospitals and universities within reach.
- Choice and opportunity — shops, culture and the chance to start a business.
Name the scale: When a question contrasts individual vs society, say which scale your point sits at — examiners reward answers that clearly separate the two.
How this is tested: Paper 2 Q1/Q4 often opens with a line graph of megacity populations or a megacities infographic (a map with figures).
You Estimate a value, Identify the fastest-growing city, Determine a range, or Describe a pattern (e.g. forecast GDP growth). Read carefully and quote the units.
| Megacity | 2000 | 2020 |
|---|---|---|
| Tokyo | 34 | 37 |
| Delhi | 16 | 31 |
| Shanghai | 14 | 27 |
| Lagos | 7 | 14 |
| Mumbai | 16 | 20 |
IB-style question — read the figure
Using the table above: (a) estimate the population of Delhi in 2020 [1]; (b) identify which megacity grew fastest between 2000 and 2020 [1]; (c) describe the overall pattern of growth shown [2].
How to answer each part
- (a) Estimate Delhi 2020. Read Delhi's 2020 column -> about 31 million. Always give the unit.
- (b) Identify the fastest-growing. Compare the rise for each city. Delhi rose from 16 to 31 (+15m) and Lagos doubled (7 to 14, +7m) — Delhi gained the most people, so Delhi grew fastest by size.
- (c) Describe the pattern. Almost every city grew, but the Asian and African cities (Delhi, Shanghai, Lagos) grew fastest, while Tokyo barely changed (34 to 37) — it is already large and in a high-income country.
Final answer
(a) ~31 million; (b) Delhi (largest gain, +15m); (c) most grew, fastest in Asia/Africa, slowest in Tokyo.
Identify vs Estimate vs Determine: Identify = read a value/label straight off. Estimate = a sensible figure from the axis. Determine = work out a value (e.g. a range = highest minus lowest).