Bright lights, big city ... and few kids

America's cities grew up as enclaves that harbored working families. In recent decades, some became neglected wastelands. Now they are again recasting themselves, this time as adult theme parks brimming with bistros, boutiques, and corner cafes. But while they're attracting a new urban elite, all the upper-class amenities are starting to crowd out families.

The urban evolution is most obvious, perhaps, in San Francisco: Restaurants here claim international renown, even as most public schools are seen as barely adequate. Then there's Seattle - home of the modern American coffee bar and a place where, more than any other US city, residents live alone.

The trend is most pronounced in these silicon capitals, yet its seeds spread much wider, observers say. At its heart is a tectonic sociological shift, as an unprecedented number of young, affluent people delay - or forgo - having children. That leaves more young people, with more disposable income, looking to live in a neighborhood with theaters showing Sartre and in houses gleaming with hardwood. In these emerging adult playgrounds, families have the means to stay, leaving cities effectively childless - and split between areas of extreme poverty and the expanding domain of the urbane and upwardly mobile.

"Cities will evolve differently because they will become more and more specialized as boutiques," says Joel Kotkin, author of "The New Geography." "The city will be a place people live for lifestyle reasons."

For the most part, that is already true in San Francisco, where 14.5 percent of residents are under 18 - the lowest figure of any major US city. Little about this city is practical or convenient for families. But its vistas, its theater and opera, and its array of every cuisine from Afghan palaw to Vietnamese pho make it a real-world Epcot Center, save the garish silver globe.

"It's a resort," says Kevin Starr, California's state librarian, who was born and raised in the city. "If I told you that Monte Carlo was losing children, would you be surprised?"

San Francisco has always been more single than the rest of the nation, and its relatively large homosexual population most likely plays some part in the low number of children. Most experts, though, are inclined to look at factors they see as more fundamental.

In recent decades, a town of bohemians tempered by stevedores, welders, sailors, and their families has become a town of bohemians amplified by the young and adventurous. The dotcom boom has only accelerated the situation. What's more, many of these newcomers are simply not interested in starting families. "I don't think there's ever been a case with so many people choosing to not have kids in times of prosperity," says Mr. Kotkin.

This is a worldwide phenomenon, he and others say, fueled by kids from divorced families afraid of commitment, women putting motherhood on hold for their careers, and couples simply not willing to make the financial sacrifice for a child, among other things.

In fact, San Francisco has more dogs than children, and the two groups have frequently clashed over access to the city's parks. When dog owners have been asked to leash their hounds for children's safety, some have responded with quips like "Leash your toddler."

More often, though, parents' challenges come from more basic concerns. "The reason we have the lowest percentage of children is that it's so expensive here," says Rick Spear, executive director of the San Francisco Children and Family Commission.

Theresa would agree. As she watches her preschool-age son, Dominic, skitters down a stone slide carved into a Golden Gate Park hillside, the single mom says finances may make her leave the city by the bay. "It's a little different here than anywhere else because it's so expensive," she says. "Everything's expensive: daycare, schools, housing."

Most anywhere is less expensive than San Francisco, but its problems are felt - in varying degrees - across the country. Parts of Chicago and Philadelphia have seen their share of children drop, and the mayor of Austin, Texas, has sought a tax break to keep families who need more living space from moving to the suburbs.

That, however, has been hard to do. Of the 25 biggest cities in the US, Austin was one of seven that saw its percentage of children drop during the past 10 years. Many cities are experiencing the same demographic forces that are at work there.

"If you spin this out into the future, you get a school district where schools [even in well-to-do areas] are dealing with urban ills because more and more of the people living there are not the ones feeding its students," says Ryan Robinson, demographer of the city of Austin.

The sense of community in a city can change, as well. Like San Francisco, Seattle has seen its character shift from a blue-collar port town to one of the priciest and most desirable cities in the nation. As the middle-class families left, monied singles and empty nesters moved in, opening a wide gulf between some of the wealthier residents and the destitute who were left behind.

"It's creating definite cultural tensions between the extremes," says Walt Crowley, a 40-year Seattle resident who runs a website devoted to local history. "Even then the 1960s, with race tensions, class tensions, and Vietnam, there was still an overriding sense of community that kept the lid on, and that has been fragmented and removed."

Children are vital to this cohesive sense of community, others add, and San Francisco is exploring ways to end the under-18 exodus. The city, for instance, is holding town meetings and focus groups, and citizens last year overwhelmingly passed a citywide ballot to earmark more money for children's issues. Indeed, San Francisco spends more per capita on its children than any US city.

"There's a real consciousness that having a viable child and family population is critical to the health of the city," says Deborah Alvarez-Rodriguez of the Department for Children, Youth, and Their Families. "One of the big things that children and families bring to a city is hope and a sense of selflessness. All the things that make the city wonderful require a next generation to fuel them."