Via The Economist, an article on how the great cities of Africa and Asia are spreading fast:

INSIDE, Essa Mwaitulo’s house on the edge of Dar es Salaam is the picture of middle-class African domesticity. The sofas are luxurious; the curtains are golden; the walls are shocking pink; the floor, on which Ms Mwaitulo’s daughter has crashed out, is polished stone. “We are free, actually,” she says contentedly, sounding like anyone who has ever moved from a rented city-centre flat to a suburban house of her own. “I can do whatever I want.”

Step outside, though, and the impression of harmony and control dissolves. The scene around Ms Mwaitulo’s house in Mikwambe is chaotic. Houses are rising higgledy-piggledy. Many are half-finished and look abandoned, although they are not: one has no floor and a tree growing inside. What appears to be a small village square turns out to be a plot on which the owner has not yet got around to building. The neighbourhood has only one paved road, no central water supply and no sewer. It is a kind of bourgeois shanty town.

A huge and growing number of people live somewhere like Mikwambe. Between 2005 and 2015 the world’s cities swelled by about 750m people, according to the UN. More than four-fifths of that growth was in Africa and Asia; specifically, on the fringes of African and Asian cities. With few exceptions, cities are growing faster in size than in population. Lagos, the capital of Nigeria, is typical: it doubled in population between 1990 and 2010 but tripled in area. In short, almost all urban growth is sprawl.

In some ways African and Asian cities are following American and European ones. London, Paris and New York all sprawled in the 19th and early 20th centuries while their inner-city slums hollowed out, as though giant hammers were beating the cities from above. The population of Paris increased almost 20-fold between 1800 and 2000 as the metropolis expanded more than 200 times. Commentators wrung their hands: London was likened to an invading army and a giant octopus.

Not like Levittown

Next to today’s fast-growing cities, though, it was a rather tame octopus. London took two millennia to grow from fewer than 50,000 people to almost 10m; Shenzhen in China managed that within three decades. And most African and Asian cities are growing more chaotically. Although no two are quite the same, their suburbs tend to be unplanned, with scant space for roads, let alone public parks. Many new suburbanites have a weak claim on the land they build upon. To planners the sprawl seems haphazard, and it has bad consequences, especially in Africa. But it has a logic of its own, and in any case cannot be wished away. Like it or not, this is how the great cities of the 21st century are taking shape.

Dar es Salaam is a case in point. The British governors who ran Tanzania (then called Tanganyika) until the 1960s envisaged it as a small, orderly city. With 5m people, population growth of more than 5% a year and some of the world’s worst traffic jams, it is now neither of those things. And the colonial rulers made another assumption, with great consequences for the modern metropolis, says Wolfgang Scholz of the Technical University in Dortmund. The city was to be planned, with Western-style owner-occupied homes on large plots, at least in the European areas. The countryside beyond was to be unplanned and African, with property owned collectively.

Dar es Salaam has swelled so much that almost all building is now in what is technically countryside. Land there can be bought and sold, but only informally; commercial developers will not touch it. The buyers, largely families moving out of the city centre, cannot encumber land that they do not truly own, so they cannot obtain mortgages. They build slowly, adding bricks when they can afford them. The urban fringe is littered with “almost houses” and shops selling building supplies. Ms Mwaitulo’s house, which was financed partly by personal loans, was built in four years—fast by local standards.

If house-building is slow, installing roads and other infrastructure is much more so. When Ms Mwaitulo arrived, Mikwambe was always dark at night. Homes now have electricity but little else. She gets water from a private borehole and sells some to neighbours. Residents cut informal deals over public space. Aisha Hassan, a farmer who sold most of her land but still lives in Mikwambe, says she asked the homebuilders who bought from her to leave space for a road. The narrow track will be woefully inadequate when the neighbourhood fills up with car owners.

It is a typical arrangement. Shlomo Angel of New York University has studied seven African cities in detail: Accra, Addis Ababa, Arusha, Ibadan, Johannesburg, Lagos and Luanda. He calculates that only 16% of the land in new residential areas developed since 1990 has been set aside for roads—about half as much as planners think ideal. And 44% of those roads are less than four metres wide.

“First the people come, then the development comes,” explains one resident of Mikwambe, a teacher in a madrassa. To an extent this is true. As the suburbs of Dar es Salaam fill up, their residents will gain officials’ ears. But retrofitting chaotic districts with roads and sewers will be slow, hard and pricey: some homes must be knocked down and their owners compensated. Dar es Salaam’s new suburbanites are less secure, and less free, than they believe.

Urbs in rure

Almost 10,000 km away, in the Chinese province of Zhejiang, another city is spreading. Working the till at a petrol station not far from where she grew up, Chen Xiaomei remembers how, two decades ago, most of Xiaoshan was farmland inhabited by peasants who seldom travelled to the city of Hangzhou, about 20km away. Now Xiaoshan is a sprawling suburb which grew from 1.77m people in 2005 to 2.35m last year. It looks nothing like Mikwambe; nor does it remotely resemble a European or American suburb.

Homes in Xiaoshan are a mixture of grubby apartment blocks and grandiose four- and five-storey homes decorated in joyous combinations of pastel colours. Locals call these “villas” and many feature European gabled fronts or Chinese pagoda roofs (or both). They are connected to the electricity grid, the sewer system and the road network. Roads account for fully 29% of land area in the newly developed suburbs of Hangzhou, according to Mr Angel. The western edge of Xiaoshan even has a subway line.

For the past two decades Zhejiang’s economic performance has been among the best in China. Hangzhou’s GDP per person reached $17,000 last year—more than double the national average. Local people who abandoned farm work for city jobs have grown richer, as have migrants from elsewhere in China. Yuan Hong, one of many people who migrated to Xiaoshan from Anhui province, north-west of the city, came to open a small electronics factory in 2004. His pot belly and the gold chain around his neck testify to its success, as does his four-storey house with an exterior of baby-blue tile.

Xiaoshan looks fairly orderly. Most roads follow a grid pattern, and buildings line the roads. Close to the urban core it has sprouted factories, car dealerships and the odd high-end apartment block. (“Money and cars,” says one shopkeeper. “That’s what we have here.”) On the fringes, though, Xiaoshan is taking on a deeply strange form. Behind the lines of tightly packed houses and apartment blocks are large fields divided into strips. A lattice of urbanity has been overlaid on an agricultural landscape.

Xiaoshan is hardly a farming titan: vendors at a nearby market say their produce is trucked in from elsewhere. The fields remain because government policy makes it hard to convert farmland into housing. So residents build their homes as large as they can and rent rooms to city workers for extra income. Although it would have been roundly condemned as ideological heresy in the days of Chairman Mao, Mr Yuan chuckles at the suggestion that peasants have become landlords. “Yes,” he says, “I suppose you could put it that way.”

Though prices have wobbled in the past few years, housing in Hangzhou is expensive. Residential floorspace sold for an average of about 16,000 yuan ($2,400) per square metre last year, roughly double the going rate in Hefei, a lower-tier provincial capital in Anhui. As a result, the pressure on land is enormous. Some people in Xiaoshan admit to having built on open land without permission, knowing that they face the risk of demolition without compensation if enforcement toughens.

So Xiaoshan is not as different from the fringes of Dar es Salaam as it appears. In both, rural areas are turning urban far faster than planners expected, making land-use laws seem ridiculous. Yan Song, who follows Chinese city planning at the University of North Carolina, says that until recently many Chinese cities were spreading because of administrative and zoning changes pushed by the central government. These days much pressure comes from below, driven by the desires of mobile people. Urban sprawl is slipping out of the government’s control.

The suburbs of Europe and North America, with their well-ordered streets and parks, increasingly seem like exceptions to the global rule. They emerged in strange circumstances: property rights were strong and rural estates were large enough to allow big housing developments. A few suburbs in the emerging world resemble them. Nuvali, south of Manila, is inspired by Irvine in California; Beijing even has a development called Orange County. But such clones tend to be for the rich, whereas the whole point of Western suburbs is that they provided middle-class people with the space and privacy once available only to the elite.

Perhaps the biggest difference is that Western suburbs emerged fully formed. Willingboro Township, on the edge of Philadelphia—the classic American suburb that Herbert Gans wrote about in “The Levittowners”—still looks much as it did when it was built in the 1950s and 1960s. Mikwambe and Xiaoshan cannot but change drastically over the years. They are opening gambits in a long, unpredictable urban game.