Global Urbanisation & the Rise of Megacities
A More Urban World
In 1950 only about 30% of the world’s people lived in towns or cities. By 2007 it crossed 50% — the first time most humans were urban — and today the figure is around 56%, heading for roughly 68% by 2050. Urbanisation is the process driving this shift. The pace, however, is uneven. Most cities in high-income countries (HICs) like the UK or Japan stopped growing decades ago and are now stable or shrinking slightly. The fastest-growing cities are in low-income countries (LICs) and newly emerging economies (NEEs) across Asia and Africa.
Around 56% of people now live in urban areas, up from about 30% in 1950. The fastest growth is in LICs and NEEs — HICs are largely stable.
Push and Pull Migration
A major driver of urban growth is rural-to-urban migration. The reasons split into two halves — push factors drive people away from the countryside, while pull factors draw them towards cities. Push factors in rural LICs include poor harvests caused by drought or soil exhaustion, lack of healthcare, few schools beyond primary level, low wages from subsistence farming, and conflict or land disputes. Pull factors in growing cities include the chance of paid work in factories or services, better hospitals and universities, mains water and electricity, and the simple hope of a better future for children.
Geographers usually describe migration as ‘push and pull’, but in reality the two work together. A failed harvest pushes a family off the land, but they also need a city they have heard about — from relatives, radio or social media — to pull them in. This is why migration tends to follow established routes: brothers join brothers, villages send chains of cousins to the same neighbourhood. The first migrant takes the biggest risk; everyone after follows a path that already exists.
Natural Increase
Migration alone does not explain the size of urban growth. Cities also grow from inside, through natural increase — the gap between births and deaths. Recent migrants tend to be young adults of working age. Once settled, they have children, and city hospitals mean those children are far more likely to survive than in a rural village. The death rate falls because clinics, vaccinations and clean water are nearby, while the birth rate stays relatively high. The result is a population that doubles itself every generation, with no extra migration needed.
The Rise of Megacities
When a city’s population passes 10 million people it earns the label megacity. In 1970 there were just three: Tokyo, New York and Osaka. By 2024 there were more than thirty, and the United Nations expects over forty by 2030. The geography of this growth is striking. Almost all the new megacities are in Asia (Delhi, Dhaka, Karachi, Shanghai), Africa (Lagos, Cairo, Kinshasa) or Latin America (São Paulo, Mexico City). The HIC megacities — Tokyo, New York, London — were among the first; the rest of the rapid growth has shifted decisively to the global South.
A megacity has 10 million or more people. There are now over thirty — most in Asia and Africa. Lagos, Delhi and Shanghai are key examples; Tokyo remains the largest at over 37 million.
HIC vs LIC/NEE: Two Different Stories
Cities in HICs and LICs are not just at different sizes — they are at different stages of a long process. Most HIC cities went through their fastest growth during the Industrial Revolution between roughly 1750 and 1950, when factories pulled rural workers into Manchester, Birmingham, Chicago and Tokyo. Once their populations stabilised, many HIC cities saw a reverse trend: counter-urbanisation, where wealthier residents leave the inner city for quieter commuter towns or rural villages. LIC and NEE cities, by contrast, are still in the middle of their first wave — the steel-and-concrete decades when migration and natural increase together produce double-digit annual growth.
If you ran a film of London’s growth from 1750 to 1950, then sped it up and overlaid it on Lagos from 1970 to today, the shapes would look strikingly similar — rapid sprawl, informal housing on the edges, struggling sanitation and a booming working-age population. The difference is timing. Lagos is doing in fifty years what London did in two hundred. That speed is why services struggle to keep up: housing, water and transport need decades of investment, but in NEE megacities the population is doubling faster than the infrastructure can be built.
Why It Matters
By 2050 the world will add roughly 2.5 billion more urban residents. Almost 90% of that growth will happen in Asia and Africa. Where those people live, how their water and energy are supplied, and whether they end up in planned neighbourhoods or informal slums will shape the next century — for the climate, for the economy and for the people themselves. The next lessons drop in on Lagos, Nigeria, to see what unprecedented urban growth looks like up close.