After a 40-minute drive to the ice rink, Madison races to the snack bar while Jake drags his hockey equipment into a musky locker room.

Elbow-to-elbow, Kim and 20 other mothers strip their sons down to their Spiderman undies and strap on pads the size of sofa cushions.

"When they turn 10, they dress themselves, and moms can't come in," she says. squatting on a duffel bag to catch her breath. "None of us want to see that day. What else am I going to do — sleep?"

Kim's remark raises a second trend emerging from the UCLA data — how few people have any unstructured time.

In just one of the 32 families did the father — a freelance film animator — make a habit of taking an evening stroll with his son and daughter. Hand-in-hand, they dodged vacant lots and broken glass in Culver City while chasing bugs and making up stories.

Kim and Gary Zeiss are keeping their children busy by design. They believe it's a key to being a successful adult in a culture that rewards multi-taskers.

"You know the old saying," says Gary, a 47-year-old attorney. "If you want something done, give it to a busy person. They're learning how to be that."

A typical Monday for the Zeiss family has four or five after-school events. They are in constant touch by cell phone, Blackberry and pager.

It's very different from how they were raised in Miami in the 1970s. Gary wasn't allowed to play football; his parents feared for his safety, but he remembers feeling unchallenged.

Now he is reviving his interest in fencing, which he shares with Madison.

"The kids are doing well," he says. "They are getting good grades. They're not obese. At the end of the day, this is good for them."

Kim's mother was divorced, and Kim spent afternoons alone watching television and doing homework. Some days she would ride her bicycle 15 miles to the beach.

Now 43, she worked as a television producer at MTV and ESPN until Jake was 2. Recently she became an administrator at Madison's school. She is fond of saying that she is "producing a family."

With all the scheduling, family life begins to resemble running a small business. That means requisitioning supplies, which invariably leads to a third hallmark of the study: clutter.

Archaeologist Jeanne E. Arnold planned to treat each house in the study like a dig site, cataloging and mapping family belongings as artifacts, but there was too much stuff. Instead, her staff took photographs. Thousands of them.

By her rough estimate, the typical American family owns more than most Egyptian pharaohs.