FIFTEEN miles east of Philadelphia, Willingboro's Grand Marketplace is a chaotic place. Merchants hawk Christian T-shirts, Amish quilts, Chinese food, massages and Afrocentric literature. Salsa music blasts from a CD stall. Most of the shoppers are black; the shopkeepers are a variegated mix of blacks, Latinos, Asians, Arabs and whites, including Pennsylvania Dutch farmers in traditional garb. Welcome to bland, homogenous suburbia.

In 1960 fewer Americans lived in suburbs than in central cities or the countryside. Ten years later the suburbs had overhauled both; by 2000 they contained more people than the cities and countryside put together. Despite more than a decade of urban boosterism, beginning with sitcoms like “Friends” and “Sex and the City” and continuing with expensive efforts to spruce up downtown districts, the drift to the cul-de-sacs continues. Between 1990 and 2006 the city of Chicago added 50,000 residents, reversing a long decline. Not bad—but in the same period the sprawling metropolis outside the city proper grew by well over a million.

As they swell, the suburbs are changing. Perhaps none ever quite resembled the colourless domestic enclaves popularised by 1970s television programmes such as “The Brady Bunch”; now, they look nothing at all like them. America's suburbs are ethnically and demographically mixed—sometimes more so than its cities. Many are less dormitories than economic powerhouses. Among the most changed is one of the most famous.

Willingboro, or Levittown as it used to be known, was built 50 years ago this summer. It was created by William Levitt, who kept costs down by bringing in ready-made walls and buying cookers and refrigerators direct from manufacturers. As he boasted to Time magazine, his company was the “General Motors of the housing industry”. The new suburb was composed of self-contained neighbourhoods, each with its own school and swimming pool. Every street was reassuringly curved and shared the first letter of its name with the neighbourhood to which it belonged. Holyoke Lane, Henderson Lane and Hummingbird Lane all lay within Hawthorne Park.

One of Willingboro's first residents was Herbert Gans, a sociologist who wanted to find out whether suburbia conformed to the popular image of bored commuters and alienated housewives. His great book, “The Levittowners”, proved it did not. But Gans had to admit that Willingboro was homogenous. Virtually all home-buyers were white people in their 20s and 30s, with young children. The population was overwhelmingly lower-middle-class and less than 1% black.

These days Willingboro is two-thirds black. Although it remains child-oriented, it is no longer exclusively so. One in eight residents is now aged 65 or over. As the proportion of children has fallen, schools have been converted to other uses. One has been turned into a community centre where, on a recent Friday afternoon, an R&B band entertained a mixed-race crowd of old folk. The music drifted into a small room where Muslims, a growing presence in the neighbourhood, had gathered for prayers.

Such diversity is now common in suburbia. According to William Frey, a demographer, the white population of big-city suburbs grew by 7% between 2000 and 2006. In the same period the suburban Asian population grew by 16%, the black population by 24% and the Hispanic population by an astonishing 60%. Many immigrants to America now move directly to the suburbs without passing through established urban ghettos. Having conquered suburbia, ethnic-minority groups are now swiftly infiltrating the more distant “exurbs”.

As the suburbs become more mixed, some inner-city areas are turning less so. Los Angeles, which markets itself as the city “where the world comes together”, and New York (“the world's second home”) both added whites and lost blacks between 2000 and 2006. So many blacks moved out of Los Angeles that, were the exodus to continue unabated, they would disappear from the city around 2050. Manhattan and San Francisco lost Hispanics as well as blacks, which is remarkable given that group's speedy growth in the country as a whole. Meanwhile, the world came together on their fringes.

Gary Gates, who follows the subject at the University of California at Los Angeles, says the number of gay and lesbian couples in suburbia is also increasing. Much of this can be put down to greater tolerance: more same-sex couples are coming out of the closet, at least to census-takers. But some of it is due to migration from central cities. Atlanta, Detroit and Philadelphia all lost gays and lesbians between 2000 and 2006. The suburban counties surrounding all three cities saw increases in the number of same-sex couples, sometimes huge ones.

Why are gays and ethnic minorities moving to suburbia? The obvious answer is that they can. No suburban developer would dare bar blacks or any other group from buying houses, as William Levitt did until 1960. It has taken longer to overcome local prejudices—and the fear that behind twitching net curtains live intolerant neighbours rather than merely curious ones. Yet such anxieties are now fading. The Rev Willie James, who launched a lawsuit in 1959 that led to the desegregation of Willingboro, says overt racism is no more, and the covert kind is so covert as to be almost undetectable.

To the extent that ethnic-minority groups have needs distinct from those of whites (which they do less and less) they can increasingly meet them outside city centres. Los Angeles' best dim sum is to be found in the largely Chinese suburb of Monterey Park. Its best Indian restaurants are in Artesia, another suburb. Gays can go online to socialise, points out Mr Gates—or they can go to ordinary bars and clubs, where same-sex couples raise fewer eyebrows than they used to. Many young gays hardly see the point of pricey enclaves like Chelsea in New York or the Castro in San Francisco.

Despite recent falls, property prices in cities like Los Angeles, New York, Miami and Washington have risen far more than the national average since the mid-1990s. Many Americans find it worthwhile to move out and commute to jobs in the city. And they may not have to commute at all. The most important reason people are moving to the suburbs is economic: that is where the jobs are.

From bedrooms to boardrooms

Even when seen from a car at 65 miles per hour, Valencia does not conform to the popular image of suburbia. Drivers heading north from Los Angeles along Interstate 5 see few houses, because most are hidden behind a golf course. Instead they pass factories, warehouses and offices. It is not a bad introduction to the place. With some 60,000 jobs and 20,000 houses, Valencia boasts a better ratio of employment to homes than the city of Los Angeles. And still its businesses grow. Between 2002 and 2009 its supply of offices will have increased by half.

Valencia was designed by Victor Gruen, an architect who did as much to shape American suburbia in the 1960s as William Levitt had done in the 1950s. Gruen was an idealist: his most enduring invention, the two-storey enclosed shopping mall, was supposed to evoke a European city centre. For Valencia he devised a dense urban core and a series of neighbourhoods connected to each other and downtown via walkways known as paseos. The settlement was supposed to be orderly and self-contained, unlike the chaotic San Fernando valley just to the south. As one of the town's early planners explained, it would be “an island of reason in the path of metropolitan sprawl”.

It didn't quite work out that way. Valencia contains no building taller than six storeys and few taller than three storeys. These days the paseos are used mostly for walking dogs, and by children. Everybody else drives. Nor did Valencia prove to be economically self-contained. Each morning about half of its residents leave for jobs in Los Angeles. Roughly the same number make the reverse trip over the Santa Monica mountains to toil in Valencia's offices, sound stages and warehouses.

This is an increasingly common pattern. In a forthcoming report, Alan Berube of the Brookings Institution, a think-tank, calculates that 45% of the jobs in America's 100 biggest metropolitan areas are found more than ten miles from the downtown core. Between 1998 and 2004 fully three-quarters of all new jobs emerged in this area. Many of these new positions were filled by local people, who were delighted to drop their long commutes to traditional city centres. But more and more Americans wake up in one suburb and go to work in another. Others, including many of Google's Bay Area employees, wake up in a city and go to work in a suburb.

America's suburbs have had shopping malls since the 1950s, and factories for longer. Increasingly, though, they are centres of white-collar work. The Inland Empire, a vast, sprawling area east of Los Angeles, accounted for more than a quarter of California's new professional and business-services jobs between 1998 and 2007. Over time, Mr Berube reckons, urban and suburban employment patterns will continue to merge. Health-care providers, for example, are drifting out of city centres to serve suburbia's increasingly aged residents.

Suburbs generally have cheaper land, newer offices and less crime than city centres. Companies that want to expand may well be able to do so in situ, and will not have to look for a new building across town. In Valencia they have another explanation for the suburbs' economic success. As Jim Backer, a developer, explains: “In the end, companies tend to move where their presidents want to move.” And many presidents want to live in places like Valencia.

To those who like their cities plain, without a dash of urban grit, Valencia seems delightful. Its streets are safe and well-kept. Its purpose-built “town centre” contains shops, cafés, wine bars and art studios. Although nobody would mistake it for San Francisco, it also lacks that city's homeless problem and has more public seating. Teenagers coming out of the cinema enter a vaguely Mediterranean village square, complete with fountains, that is a far more pleasant place to linger than anywhere in, say, New York's Chelsea.

Valencia was one of the first places in America to build a shopping district that evoked an old-fashioned town centre. These days such things are popping up all over the country. Rick Caruso, a master of the genre, has built them in the heart of Los Angeles as well as in suburbs like Glendale. San Jose, in the Bay Area, has the hugely successful Santana Row, which is vaguely French, whereas Mr Caruso's developments are vaguely Italian. The popularity of such confections suggests that Americans want to spend time in places that look like cities but feel like suburbs. They hint at a broader pattern: cities and suburbs are converging. This is not entirely good news.

Trouble in Wisteria Lane

Right-thinking people disapproved of suburbs when Gans moved to Willingboro, and they dislike them today. James Kunstler, an American urbanist, says they represent “the greatest misallocation of resources the world has ever known”. Richard Florida, an influential writer, sees them as incidental, at best, to cities' highest purpose, which is to concentrate young, creative folk who will come up with brilliant innovations. Now that America worries about global warming, the acres of bungalows and freeway exit ramps seem not just pointless but harmful.

Although much of this is nonsense, it cannot be denied that a little sheen has come off America's suburbs in the past year. Especially in the West, many have been hammered by foreclosures and falling house prices. As a result, their budgets are a mess. The fact that this is largely a consequence of success—the suburbs and exurbs grew rapidly at a time when lending standards were lax, and are now suffering the consequences—is little consolation. Nor is the fact that, as Joel Kotkin of Chapman University points out, the bottom has also dropped out of the city-centre apartment market.

Other problems are creeping into suburbia. The one that its inhabitants complain most bitterly about is traffic. America has failed to build enough roads to accommodate the suburbs' growing population—a big problem for places where public transport is generally weak or non-existent. Interstate 5, which is the only practical route between Valencia and the city of Los Angeles, is often clogged. Those who make the journey in either direction pay twice as much for petrol as they did in the spring of 2004.

Another worry is crime. Since 2001 the number of violent crimes in suburban areas has risen by 10%, according to the FBI. That is no more than one would expect, given the speed of population growth there. Yet it is a poor record compared with America's big cities, which have cut violent crime by 17%. In the past few years many of America's biggest indoor marijuana farms have been discovered in the suburbs.

In some suburbs fear of crime has risen more steeply. Willingboro's violent crime rate is one-quarter of Philadelphia's, yet its teenagers enter school through metal detectors. Blacks and whites alike worry that new arrivals from Philadelphia and Camden, in New Jersey, are importing gang culture. “They come here to escape, and sometimes they don't leave all their baggage behind,” explains Reva Foster, who works for Willingboro's government.

Perhaps the greatest problem of all is demographic. The suburbs used to be blessed with a young, productive population. Many of the newer, more distant exurbs still are. These days, though, many suburbs built in the 1950s are older than the central cities they surround. Willingboro's growing army of retirees is straining city services and resisting increases in property taxes, which account for almost two-thirds of the town government's revenues. Willingboro desperately needs to improve its schools if it is to continue attracting affluent settlers. Yet it is finding it ever harder to persuade residents to pay for them.

Although many urban mayors would happily swap the suburbs' problems for their own, cities do have one advantage: they tend to have large, centralised governments. In states like New Jersey, many suburbs try to govern themselves and suffer from diseconomies of scale. With just 33,000 residents Willingboro runs its own schools, police force, fire service and public-works department, among many other things. Elsewhere suburbs are controlled by urban city halls that largely ignore them, except as generators of taxes. Both arrangements make it difficult to come up with bold cures for the suburbs' growing pains.

An ordinary place

Weak government is a particular problem because, as suburbs become less homogenous, they are also losing some of their cohesiveness. A big complaint in Willingboro is that neighbours are less sociable than they used to be. Levitt's ideal of self-contained neighbourhoods is largely forgotten: most of the pools have closed, and children may no longer attend their local school. Jim Gray, a longtime resident, complains it is ever harder to rustle up volunteers for civic events. On the other hand, the same could be said of almost anywhere in America. Willingboro has managed to arrange about a dozen events to celebrate its 50th birthday.

Walk around Willingboro in the evening and you will see homeowners mowing their lawns and children squirting each other with water pistols, just as they did when the neighbourhood was much more homogenous. Mr Jones, the pastor, calls it “an ordinary place”, which is an excellent description. It is a reflection of the resilience of the suburban model that such places have changed dramatically while remaining essentially humdrum. At their best, they are even rather dull.