World urbanisation

Urbanisation is the increase in the proportion (percentage) of a population that lives in urban areas (towns and cities) rather than in rural areas.

It is measured as a rising share of people living in urban settlements over time, and globally it is driven mainly by rural-to-urban migration and natural increase.

Suburbanisation is the movement of people (and businesses) out from the crowded, expensive inner city to the suburbs on the edge of the same urban area. People still live within the city region and typically commute back to the centre for work, but gain more space and cheaper housing.

Counter-urbanisation is the movement of people beyond the city altogether, into smaller towns and rural areas in the countryside, usually for a better quality of life, more space and a quieter environment (increasingly enabled by cars, motorways and remote working).

The key difference is how far people move: suburbanisation stays within the urban area (edge of the city), whereas counter-urbanisation moves people out of the city into rural areas.

Challenge 1 — housing shortages and informal settlements. Because cities grow faster than formal housing can be built, many newcomers end up in slums / informal settlements (e.g. Kibera, Nairobi), living in overcrowded, self-built homes on unsafe land with insecure tenure. This creates poor living conditions and the risk of eviction.

Challenge 2 — inadequate water, sanitation and services. Rapid, unplanned growth means clean water, sewerage, electricity, waste collection and healthcare cannot keep up with demand. Many people share few toilets and lack safe water, so waterborne diseases (such as cholera and diarrhoea) spread, while air pollution and traffic congestion worsen as the city expands.

Both challenges arise from the same root cause: the speed of growth outpaces the provision of housing and infrastructure, so people are housed and served informally rather than formally.

The resource shows a strong upward trend in world urbanisation. The share of people living in urban areas rose from about 30% in 1950 to about 55% in 2020 — an increase of roughly 25 percentage points, meaning the world passed the point where more than half its population is urban. The trend is projected to continue rising to about 68% by 2050, so urbanisation is not slowing.

There is also a clear difference in pattern between region types. The line for less-developed (LIC/NEE) regions rises far more steeply after 1980 than the line for more-developed (HIC) regions. This shows that recent and future urbanisation is being driven mainly by the developing world (especially Asia and Africa), whereas the more-developed regions urbanised earlier and their line is now flatter / more stable because they are already highly urban.

Explanation of the pattern. LICs and NEEs are urbanising rapidly now because of rural-to-urban migration (rural poverty and mechanisation pushing people out; city jobs and services pulling them in) plus high natural increase from young urban populations. HICs urbanised during their earlier industrialisation and have since moved into suburbanisation and counter-urbanisation, so their urban proportion is high but changing little.

Overall the resource shows rising global urbanisation, the crossing of the 50% threshold, continued growth to 2050, and a shift in where that growth occurs — from more-developed to less-developed regions.

Description of the change. The resource shows a rapid rise in the number of megacities, from just 3 in 1975 to over 30 by 2020 — a roughly ten-fold increase in 45 years. There has also been a clear shift in location: in 1975 megacities were in high-income countries, but by 2020 most are in Asia and Africa (the developing world), with Lagos and Dhaka highlighted as among the fastest growing.

Explanation of the number rising. More cities have passed the 10-million threshold because rapid urbanisation in LICs and NEEs is driven by rural-to-urban migration (push factors such as rural poverty and loss of farm jobs; pull factors such as urban jobs and services) combined with high natural increase, because migrants are young and have high birth rates. Together these swell city populations quickly.

Explanation of the shift in distribution. The move of megacities to Asia and Africa reflects the fact that HICs urbanised earlier and their cities have stabilised (even losing inner-city population to suburbanisation and counter-urbanisation), whereas LICs and NEEs are urbanising now. Rapid economic change, industrialisation and, in some cases, urban primacy (one dominant city attracting most investment and migrants) concentrate huge populations into a few cities such as Lagos and Dhaka.

Overall the resource shows megacities becoming more numerous and increasingly located in the developing world, mirroring where the fastest urbanisation is now taking place.

The stage and speed of urbanisation differ sharply between HICs and LICs/NEEs, because they industrialised at different times and are at different points in the urban cycle.

High-income countries urbanised early and are now stable. HICs such as the UK experienced rapid urbanisation during their 19th-century industrialisation, when rural people moved into growing industrial cities for factory work. They are now highly urban (typically 80%+) but their urban proportion is changing slowly, because they have moved on through the urban cycle: suburbanisation (residents moving to the edge as car ownership and incomes rose), counter-urbanisation (some moving beyond the city into rural towns for quality of life) and re-urbanisation (people returning to regenerated inner-city areas, e.g. former docklands converted to flats and offices). Growth is therefore managed and de-centralising, then re-centralising, rather than explosive.

Low-income and emerging countries are urbanising rapidly now. In much of Asia and Africa the urban proportion is rising steeply, driven by rural-to-urban migration (push: rural poverty, mechanisation, lack of services; pull: city jobs and services) plus high natural increase from young migrant populations. This produces very fast, often unplanned growth, so cities can outpace housing and infrastructure, producing informal settlements (slums) such as Dharavi (Mumbai) or Kibera (Nairobi), congestion and strained services. Many of the world's new megacities (Lagos, Dhaka) and cases of urban primacy are found here.

In conclusion, the key differences are timing and speed: HICs urbanised early and slowly and are now in a stable, de-centralising phase, whereas LICs/NEEs are urbanising later but far faster, creating major management challenges. The underlying process (migration + natural increase) is similar, but its pace and the ability to plan for it differ, which is why rapid urban growth and slums are concentrated in the developing world.

A megacity is an urban area of over 10 million people, and most of the world's fastest-growing megacities — such as Mumbai, Lagos and Dhaka — are in the developing world, where growth is exceptionally rapid. This essay examines why that rapid growth creates such severe management challenges, before judging where the greatest difficulty lies.

The central problem: growth outpaces provision. Megacities in LICs/NEEs grow through rural-to-urban migration plus high natural increase, adding people far faster than housing, water, sanitation, transport and jobs can be provided. The result is that much of the city develops informally. In Mumbai, this is seen in Dharavi, one of Asia's largest informal settlements, where hundreds of thousands live in overcrowded, self-built homes on a small site. Managing a city is far harder when a large share of it is unplanned.

Housing and informal settlements. The most visible challenge is housing. Rapid growth means authorities cannot build enough affordable homes, so slums/informal settlements spread onto unsafe land (floodplains, steep slopes, railway edges), often with insecure land tenure. This makes it difficult to provide services and creates the risk of eviction, as in Dharavi (Mumbai) and Kibera (Nairobi).

Basic services — water, sanitation and health. Rapid growth overwhelms water supply and sewerage. In informal areas many people share few toilets and lack safe water, so waterborne diseases (cholera, diarrhoea) spread. Waste collection, electricity and healthcare also fail to keep pace, lowering quality of life and life expectancy. Providing these to millions of new residents each year is a huge and continuous burden.

Transport, congestion and pollution. As megacities sprawl, traffic congestion and air pollution worsen (e.g. severe congestion and poor air quality in Lagos and Dhaka). Congestion wastes time, harms health and holds back the economy, and building mass transit is expensive and slow relative to the pace of growth.

Employment and the economy. Rapid growth means formal jobs cannot absorb everyone, so many work in the informal economy (street trading, recycling, small workshops) with low, insecure incomes — although this does provide vital livelihoods and, in Dharavi, considerable economic output.

Which challenge is greatest? Many of these problems share a single root — the speed of growth outstripping planning and funding. Housing and sanitation are arguably the most fundamental, because poor housing and lack of clean water directly threaten health and safety, and they underpin the other problems. However, the challenges also compound one another: informal housing has no sewerage, which spreads disease; sprawl worsens congestion; and weak governance and limited money in many LICs make every problem harder to solve.

Conclusion. The rapid growth of megacities creates major management challenges primarily because growth outpaces the provision of housing, services and infrastructure, forcing much of the city to develop informally — as Dharavi (Mumbai) and Lagos show. The single greatest challenge is arguably housing and sanitation, since these directly affect health and safety, but the deeper issue is that rapid, continuous in-migration and natural increase, combined with limited funds and governance capacity, mean the city is always trying to catch up. Management is therefore most effective when it works with this growth — for example through slum upgrading and phased service provision — rather than trying to stop it.

Rapid urban growth in low-income and emerging cities creates severe challenges — housing shortages, informal settlements, poor sanitation, congestion and pollution — but a range of management strategies exists. Using Mumbai (India) and its Dharavi settlement, this essay assesses how far these challenges can be successfully managed, weighing what management can and cannot achieve.

The scale of the challenge in Mumbai. Mumbai is a megacity of over 20 million whose growth, fuelled by rural-to-urban migration and natural increase, has outpaced formal housing. The result is large informal settlements, of which Dharavi is the best known: hundreds of thousands live on a small, densely packed site with overcrowded, self-built housing, inadequate sanitation, limited clean water and a huge informal economy (recycling, pottery, textiles) generating significant output but insecure incomes.

Strategies that can succeed. Several approaches have improved conditions:

• Slum upgrading and site-and-service schemes. Rather than demolition, authorities provide legal tenure, clean water, sanitation, drainage, electricity and paved paths, allowing residents to improve their own homes incrementally. This is relatively cheap, keeps communities and livelihoods intact, and has measurably improved health and living standards where applied.
• Transport investment. Expanding suburban rail, metro lines and roads improves mobility and can reduce congestion and pollution, connecting poorer residents to jobs.
• Planning and sustainable approaches. Affordable-housing schemes, land-use planning and greener (eco-city) design (green space, better drainage, waste recycling) tackle growth more sustainably and reduce flood and health risks.
• Working with the informal economy. Recognising and supporting informal enterprises (as in Dharavi) protects livelihoods while conditions are improved.

Limits to successful management. However, success is partial and constrained:

• Funding and scale. The number of people needing housing and services is enormous and rises continuously, so schemes struggle to keep pace; upgrading a few areas does not solve city-wide shortages.
• Top-down redevelopment can backfire. Large demolition/redevelopment projects (e.g. proposals to redevelop Dharavi) risk displacing the poor, breaking up communities and destroying informal livelihoods, and can stall for years over cost and consent.
• Governance and inequality. Weak governance, corruption and limited budgets mean strategies are unevenly implemented, and gains can be captured by wealthier groups.
• Continued in-migration. Because the push and pull factors driving migration remain, the city keeps growing, so management is always trying to catch up.

Conclusion. The challenges of rapid urban growth in Mumbai can be significantly reduced, but not fully solved, by management. The most successful strategies are participatory slum upgrading and service provision that work with residents and their livelihoods, supported by transport and planning; these have clearly improved conditions in parts of the city. Yet because funding is limited, in-migration continues and top-down redevelopment can displace the poor, a residual challenge always remains. The most accurate assessment is therefore that management can make rapid urban growth far more liveable and sustainable — improving housing, services and health — but cannot eliminate the underlying pressures, so it must be continuous, well-funded and community-based to succeed.

Rapid urban growth in low-income and emerging countries has two main drivers — rural-to-urban migration and natural increase. This essay assesses the extent to which migration is the main cause, weighing it against natural increase and other factors before reaching a judgement.

The case that rural-to-urban migration IS the main cause. In the early stages of rapid urbanisation, migration is often the dominant force. Large numbers move from the countryside to cities such as Lagos and Mumbai, pushed by rural poverty, the mechanisation of farming (reducing farm jobs), drought and a lack of services, and pulled by the prospect of better-paid urban jobs and services (schools, hospitals, electricity, the 'bright lights'). This migration adds people to the city directly and quickly, and it is what causes cities to swell faster than housing can be built, producing informal settlements like Dharavi (Mumbai). Because it is rapid and can be very large, migration clearly drives the initial explosive growth.

The case that natural increase is at least as important. However, migration is not the whole story. Migrants are typically young adults of child-bearing age, so once they settle, cities experience high birth rates, while improving urban healthcare lowers death rates — producing strong natural increase. Over time, as a city becomes established, natural increase often overtakes migration as the main source of growth, because the young population that migration brought in then has children. So migration and natural increase are linked: migration seeds the natural increase that follows.

Other contributing factors. Growth is also affected by economic development and industrialisation (creating the urban jobs that pull migrants), by urban primacy (one dominant city, e.g. Lagos, concentrating growth), and by reclassification (as settlements grow, rural areas are re-defined as urban). These interact with migration and natural increase rather than replacing them.

Conclusion. On balance, I partly agree: rural-to-urban migration is usually the main trigger of rapid urban growth, especially in the early, fastest phase, and it is what overwhelms housing and services (Lagos, Mumbai). However, the statement is too simple. As cities mature, natural increase frequently becomes the larger component, and the two are inseparable because migration brings in the young population that then drives natural increase. The most accurate view is therefore that migration and natural increase act together, with migration typically dominant at first and natural increase growing in importance over time — so migration is a main cause, but rarely the only one.