IB ESS SL8.2 Urban Systems & Urban PlanningPaper 1 & 2~13 min read
Why Cities Grow
For almost all of human history, most people lived in the countryside. That flipped about fifteen years ago. Today more than half of us live in towns and cities, and the share is still climbing. This page is about why people move, and what stage of that journey different countries are at.
📘 What you need to know
Urbanisation is the process where a growing proportion of a country’s population lives in urban rather than rural areas.
According to the World Bank, about 56% of the world’s people — roughly 4.4 billion — now live in towns and cities.
Rural-urban migration is the main driver. It is mostly internal migration, within one country.
Push factors make people leave rural areas. Pull factors attract them to cities.
Migration can be voluntary (a choice) or forced (war, famine, disaster).
The urbanisation pathway has five stages, from a rural society through rapid growth to counter-urbanisation.
Level of urbanisation and rate of urban growth are not the same thing.
Deurbanisation is the reverse: people moving back out to rural and suburban areas.
What urbanisation actually means
Urbanisation is the process where a growing proportion of a country’s population moves from rural areas (the countryside) to urban areas (cities and towns).
Notice the word proportion. It is a share, not a headcount. A country’s cities can gain a million people and its level of urbanisation can still fall, if the rural population grew even faster.
DefinitionUrbanisation — the increase in the proportion of a population living in urban areas.
As urbanisation happens, land becomes more built up, with infrastructure, housing and industry taking over the landscape. Cities expand, they develop denser populations, and they see more continuous human activity — traffic, lighting, noise and heat that never really stop.
Look at the shape, not just the crossing point. Rural population is close to its peak, while the urban line shows no sign of levelling off.
If a question gives you a graph like this, describe it in three moves: the overall trend, a figure with units pulled off the axes, and anything unusual such as the crossing point. Those three moves earn most of the marks on any data-description question.
Rural-urban migration
Rural-urban migration is the movement of people from the countryside into cities, and it is the biggest single driver of urbanisation. Most of it is internal migration, meaning people move within their own country rather than across a border.
People move looking for better living conditions, job opportunities and safety. The effect is that the urban population grows, often at the expense of the rural one. In China, rural-urban migration has driven enormous city growth, with people leaving farming regions for factory and office work in cities such as Shenzhen and Beijing.
Push and pull factors
Push factors are the reasons people leave rural areas. Pull factors are the attractions of the city that draw them in. Most real migrations are a mix of both.
Some pull factors are real and some are only hoped for. Many migrants arrive to find the jobs and housing are not there.
Add this and stand out. Migration is not the only reason cities grow. Cities also grow by natural increase, because the people who migrate tend to be young adults, and they go on to have children in the city. Urban growth = migration plus natural increase.
Voluntary and forced migration
Type
What it means
Example
Voluntary migration
People choose to move to cities for better opportunities or living conditions
Workers moving from rural China to Shenzhen for factory jobs
Forced migration
People are pushed into cities by circumstances such as war, famine or natural disaster
Refugees fleeing the conflict in Syria and settling in urban areas of Turkey and Jordan
The urbanisation pathway
Countries become more urban as they develop economically. That transition, from a low income country to a high income one, can be drawn as a pathway over time with five stages. The pace speeds up in the middle, then slows and flattens, and may even fall once counter-urbanisation gets going.
The curve is an S shape. Slow at the start, very steep in the middle, then flattening near the top because there are hardly any rural people left to move.
Stage
What is happening
Urban share
1 Developing
A rural society. Most people are subsistence farmers and urbanisation is low
Low and flat
2 Emerging
Economic take-off begins. Rapid rural-urban migration leads to an accelerating rate of urbanisation
Rising quickly
3 Emerged
A maturing economy. Rates of urbanisation still rise but start to slacken off, and suburbs spread outwards
Around half
4 Developed
Mass urbanisation in most developed nations. The rate levels off and the urban percentage peaks. Most people now live in towns
High, near the peak
5 Counter-urbanisation
In advanced economies decentralisation sets in. People move to smaller towns and semi-rural areas, although urban ways of living keep spreading
Flat or slightly falling
Level versus rate
This one catches people out every year, so slow down here.
The level of urbanisation is the share of the population that already lives in urban areas. It is a snapshot.
The rate of urban growth is how fast that urban population is increasing. It is a speed.
Developed countries such as the UK, Germany and the USA have high levels of urbanisation but low growth rates. Their towns and cities are already built and nearly everyone already lives in one. Emerging and developing countries such as China, India and Nigeria have lower levels of urbanisation but high growth rates — they are still building their cities right now.
🧩
Level is a photo, rate is a video
A photo tells you where a country is standing. A video tells you how fast it is moving. A country can be standing high up and barely moving (the UK), or standing lower down and sprinting (Nigeria).
Deurbanisation
Deurbanisation is the reverse process: people moving out of cities and back to rural or suburban areas. Three things drive it.
Overcrowding — cities become too congested, the cost of living climbs and living conditions get worse.
Improved rural opportunities — rural areas develop better services, jobs and housing, so there is less reason to leave.
Technological change — with remote working, people can live in a rural area and still work for an urban company.
Deurbanisation, counter-urbanisation and stage 5 of the pathway are all describing the same movement of people. Use whichever term the question uses, and you will be safe.
Worked examples
WE 1
Push and pull factors
Outline two push factors and two pull factors of rural-urban migration. (4 marks)
Push factor 1Poverty in rural areas, with few jobs available and low wages for the work that exists.
Push factor 2
Natural disasters such as drought or flooding make farming unreliable, so families lose their income.
Pull factor 1
Cities offer more jobs and better pay, especially in industry, services and trade.
Pull factor 2
Better access to healthcare, education and housing than is available in the countryside.
Push = problems in rural areas; pull = attractions of the citysay clearly which factor is which — do not leave the examiner guessing
WE 2
Describing an urbanisation graph
Describe the trends shown in world urban and rural population between 1950 and 2050. (4 marks)
Trend 1: urban population
The urban population rises continuously, from under 1000 million in 1950 to a projected figure of over 6000 million by 2050.
Trend 2: rural population
The rural population rises more slowly, then levels off at around 3400 million and begins to fall after about 2020.
Trend 3: the crossing point
The two lines cross at roughly 2009, so from that point on more of the world’s population is urban than rural.
Overall
The gap between the two lines widens steadily after the crossing point.
Urban rises throughout, rural flattens, and the lines cross around 2009always quote at least one figure with its unit — a description with no numbers loses marks
WE 3
Level and rate
Explain why a country can have a high level of urbanisation but a low rate of urban growth. (3 marks)
Point 1: what a high level means
A high level of urbanisation means most of the population already lives in towns and cities.
Point 2: why growth then slows
Because so few people are left in rural areas, there are not many more who can migrate in, so the urban population grows only slowly.
Point 3: the example
Countries such as the UK are at stage 4 or 5 of the urbanisation pathway, where their cities are already built and some people are even moving back out.
High level = already urban; low rate = little room left to growa named country turns a general answer into a secure one
💡 Exam tips
Learn the figure: about 56%, or 4.4 billion people, live in urban areas (World Bank).
Keep level of urbanisation and rate of urban growth completely separate in your answer.
Know all five stages of the urbanisation pathway by name, and which type of country sits at each one.
Have named examples ready: China for rural-urban migration, Syria for forced migration.
When describing a graph, give the overall trend, a figure with units, and any turning point.
Remember cities also grow by natural increase, not migration alone.
⚠ Common mistakes
Saying urbanisation means cities getting bigger. It means the proportion of people living in urban areas is increasing.
Confusing level with growth rate. Developed countries have high levels and low rates; developing countries are often the other way round.
Treating all migration as voluntary. Forced migration from war, famine and disaster also fills cities.
Assuming rural-urban migration is international. It is mostly internal, within one country.
Forgetting pull factors can be a perception. The jobs and housing people expect are not always there.
Ignoring deurbanisation. In advanced economies the flow can and does reverse.
Up next: Urban Sprawl and Expansion. Cities that grow this fast have to grow outwards, and that is where the environmental damage starts.
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