One & Only : With both parents on the go and financial resources limited, it is increasingly likely their child will remain their. . .

Baby boomers may want to have it all, but more of them, it appears, are settling for less as boom-age parents opt for the one-child family.

In the past 30 years the number of single-child households has increased steadily, to about 15% of all households with children by 1989, according to Census Bureau figures. And by the end of the century, experts predict, that figure could rise to 25%.

The trend ties in neatly with a distinctly ‘90s practicality:

With less money, time and space, having just one child makes good sense to many. And although myth sometimes depicts them as selfish, spoiled and socially handicapped, only children may have numerous advantages over children with siblings.

“Only children are almost becoming idealized by the two-career couple,” says Toni Falbo, a researcher from the University of Texas at Austin who has studied only children for 17 years.

Diane and Dan Barrows of Los Angeles are one couple who decided to have just one child. Their son, Robbie, is 4.

The Barrowses, in their mid-40s, say they feel too old to begin raising a second child. They also wonder whether their financial resources would stretch to cover privileges, such as private school, for two children.

In addition, both parents work full time, and Diane Barrows says she cannot imagine dividing between two children the few hours she now devotes to Robbie.

“You can get around the financial problem. But the time problem is very difficult,” she says. “When we grew up, only children were very rare. But I think a lot of people are starting to realize they don’t have the resources” for more than one child.

Indeed, today’s parents of only children usually have just one by choice and are likely to have considered the effect that family size will have on each member of the household.

Nevertheless, some baby boomers, with characteristic Angst, seem to have trouble reconciling their desire for only one child with other expectations. Because most grew up with a sibling--or two or three--that adds to the “discomfort factor” in limiting their family, says Ellie McGrath, the author of the book “My One and Only: The Special Experiences of the Only Child.”

“Having a child is the greatest thing I ever did in my life,” says Barbara Campbell, a 37-year-old actress who lives in Van Nuys. “But I never thought I would have just one. What I miss most about not having more than one child is that big sense of family.”

Campbell, who grew up with four siblings, and her husband, Ken, who has three, still have not made a final decision about the size of their family. Their daughter, Molly, is 7.

“We think about having another one all the time,” Campbell says. “But that thought gets a little dimmer every year.”

A reticence to depart from tradition haunts many young parents, McGrath says. “Most people tend to think that the ideal size is the same size of the family they grew up in,” she says. “They want what they experienced.”

Researchers say society’s views of one-child families have fluctuated over time. Early in the century, many books on child-rearing suggested there was something “defective” about an only child, Falbo says.

But “it wasn’t a matter of choice back in our parents’ time,” says Michele Slung, the author of “The Only Child Book,” which contains memoirs of famous only children. “There wasn’t contraception, and you couldn’t decide ahead of time whether you were going to have a family.”

In one of the first scientific studies on the topic, in 1928, researcher Norman Fenton looked at a group of Whittier children in kindergarten through high school and found that only children seemed to be developing normally.

“He searched and searched and found that only children weren’t any different from anyone else,” Falbo says.

In fact, during the Depression, it was considered wise for a couple to limit their family to one child because of financial hardship.

“People who grew up during the Depression say it was not a big deal to be an only child,” McGrath says. “Because there were so many, it was acceptable.”

But during the post-World War II baby boom, couples with only one youngster were more likely to be regarded as odd. One study in the mid-1950s found that the primary reason parents gave for having a second child was so that the first would not be an only child.

“In the ‘50s it was really considered a selfish choice to have an only child,” McGrath says.

But like the Barrowses, Campbell says demands on time and money contribute to the need for smaller families.

“There is that time factor of being able to create a balance between work and home,” she says. “(Child rearing) takes an enormous amount of energy, and it’s a big job. But I have my own career, and my husband works.”

Being the sole recipient of their parents’ resources appears to largely enhance the lives of only children, experts say.

McGrath found that only children seem to have a head start in many aspects of development, adding that “the precocity--that stereotype of the only child is actually somewhat true.” Further, because only children have to venture outside the family for social contacts, they might become more involved in extracurricular activities, studies show.

A study of 150,000 adults and children found that only children performed better on academic tests and developed better social skills. The 1989 study, by UCLA demographer Judith Blake, showed that only children get about one-fifth more years of education than children from large families.

Indeed, education is one of the few areas where studies have shown a difference between only children and children with siblings. There appears to be little difference in personality characteristics, although McGrath also found that only children are much more likely to be straight shooters.

“Only children tend to take other people at their word because they have always had a straightforward relationship with their parents,” she says. “That can be an advantage or disadvantage. You don’t really learn how to play politics right from the start. It’s a skill you have to work to acquire as an only child, whereas if you’re in a house with siblings . . . you sort of develop these skills more naturally.”

Anne Colvin, a single parent who lives in Los Angeles, grew up with four siblings. But she says she feels her relationship with her son, Bobby, 12, is much closer than her relationship with her own parents.

“The relationship my son and I share is a lot different than what I shared with my parents,” she says. “He is more committed to me than I ever was to my parents. I’m not sure why that is. I’m his only parent. Is it because of a lack of other children or the lack of another parent?”

Still, it requires effort not to make an only child the center of the universe, Campbell says.

“(My daughter Molly) is very strong-willed, and I sometimes feel it would be good for her to have a brother or sister so that she could learn to share,” Campbell says. “She gets a lot of attention and care. But we try to make her understand she has to fulfill certain responsibilities.”

Diane Barrows says she tries hard to avoid “the only-child syndrome,” which she describes as “being ready to cater to his every need.”

“I think there is more focusing on an only child, which I think can be detrimental,” she says. “I try not to jump every time (son Robbie) calls.”

It’s equally important for parents not to heap great expectations on the child, according to Slung. “If you’re an only child and your parents dote on you, that can be a tremendous amount of pressure,” she says.

Most parents say they sometimes worry about their only child’s future, and Barrows says she thinks about her son’s life as an adult only child.

“That is a concern to me,” she says. “I can see it being a little bit lonely.”

McGrath says only children may have a difficult time in adulthood if they become the sole source of care for their aging parents or find themselves alone in their grief over the deaths of their parents. Studies show that children value their sibling relationships most deeply in adulthood, she adds.

McGrath’s interviews with only children who are now adults show that what they disliked most was the perception that they are different.

“One theme that came up a lot was that only children hate the mythology of the only child: that they are lonely, spoiled, isolated,” she says. “One of the disadvantages of being an only child is people have these negative assumptions and misconceptions about it.”

And Slung found in her interviews with famous only children that about half enjoyed their position, while half despised it.

“My ultimate belief after doing all this reading was that it was divided right down the middle,” she says. “There was no ambivalence. You either loved it or you hated it.”

But Campbell says she believes children are not affected by the lack of siblings as long as the home is a happy one.

“Ultimately,” she says, “I think kids are going to remember that they were well-loved.”