Sociologist Timothy Biblarz and his wife are raising their children in a traditional two-parent family structure, which gives a child an edge for success. However, research by Biblarz and a co-researcher found that children raised by single mothers are nearly as likely to succeed in adulthood as children raised in two-parent homes, and more likely to be successful as adults than children raised by others, including a single father.

Indeed, children raised by single mothers are even more likely to reach higher professional and educational levels than children raised in households headed by a stepfather or single father, according to Timothy Biblarz, the study's lead author and an assistant professor of sociology.

"Despite the criticisms of single mothers so frequently heard, the offspring of female heads of household tend to go further professionally than offspring from other types of nontraditional family structure," Biblarz said. "In fact, their achievements approximate those of children from two-biological-parent families."

If economic resources were the primary determinants of children's socioeconomic attainment, said co-author Adrian E. Raftery, a University of Washington sociologist and statistician, "children from father-only or stepfather-headed families would do better than children from female-headed families - but they don't."

"It may be that, on average, single mothers invest more in their offspring from a marriage that has ended, because they're less likely to have other children or stepchildren. Or perhaps a mother's nurturing presence is an emotional resource that proves even more important than financial advantages."

The USC-UW findings appear in a recent issue of the scholarly journal Social Forces.

Biblarz and Raftery and USC graduate student Alexander Bucur analyzed a survey of 22,761 American male respondents, ranging in age from 25 to 64, to learn the structure and socioeconomic level of the families in which they were raised.

All respondents were asked to report the occupation of the head of the household in which they grew up. In a traditional family, the head of household was assumed to be the father. In a nontraditional family, the head of household might, for example, be a single mother, a single father, a stepfather or another person, such as a grandmother.

First the researchers ranked these occupations on a 100-point scale - a scale that pegs the average education and income level of any given occupation. The higher an occupation on the scale, the higher the head of the household's socioeconomic status was judged to be.

The researchers then compared these rankings to the socioeconomic index (SEI) rankings achieved in adulthood by the respondents themselves.

The occupations of men from traditional families averaged an SEI of 42. Men raised in households headed by their mothers averaged an SEI of 40. So children raised by their mothers only - due to divorce, death or out-of-wedlock birth - averaged SEIs only 2 points lower than those of children from traditional two-parent homes. But with an SEI of 35, the offspring of all other types of nontraditional family structure experienced more than double the level of disadvantage.

"People talk about the negative consequences of single-mother households, but they don't consider the alternatives," Biblarz said. "Kids from other nontraditional family structures tend to fare worse."

Socioeconomic attainments of the respondents correlated significantly with what the researchers call a "Distance From Mother" scale, which calculated the number of obstacles between a child and those maternal contributions. The greater the number of obstacles, the lower the respondent's socioeconomic status ranking.

"On average, mothers tend to sustain a higher level of emotional involvement in children amid spousal conflict and marital disruptions," Biblarz said. "Compared to a father, a mother has a greater reproductive investment in any particular child. A father's relations with his children tend to diminish as his relations diminish with the children's mother."

Stepparents are another matter, Raftery said. "Relationships between stepparents and offspring are, on average, characterized by greater emotional distance and uncertainty, higher levels of conflict and lower levels of parent-to-child wealth flows. Such disadvantages do not bode well for the child's professional attainment."

The fate of children raised without mothers proves the point even more vividly.

"Compared to children raised by single mothers or both biological parents, men from nontraditional family backgrounds other than mother-headed households are almost twice as likely to occupy the lowest occupational stratum," Raftery said.

Again the power of a mother's influence on a child's economic destiny was revealed when the researchers looked at intergenerational occupational inheritance - that is, a child's tendency to follow in his parent's footsteps when selecting a career. The strength of the inheritance process is a rough measure for a family's ability to hold ground economically and socially from one generation to the next. The higher the scores on the Distance From Mother scale, the weaker a child's tendency to inherit his career from the head of the household.

"It's particularly telling that the correlation applied even to men raised by their own fathers," Biblarz said. "Given that men from intact families are most likely to follow in their father's footsteps, men raised in nontraditional families by their fathers might be expected to show high levels of occupational transmission.

"Yet the incidence of occupational transmission was lower among men from father-headed alternative family backgrounds than among men raised in households where the mother was present, including households headed by stepfathers. There's something about a mother's influence that encourages children to follow positive role models."

Compared to a two-biological-parent family background, a nontraditional mother-headed family background reduced scores on the occupational-inheritance scale by 11 percent; a stepfather-headed family, by 21 percent; a nontraditional father-headed family, by 30 percent; and an other-headed family, by 38 percent, the researchers found.

"Having a man in the house (and the added income he represents) can be a good thing, but the message here is: If you can't be with two parents, you're better off with your mother than you are with your father or anybody else," Biblarz said.

African American children are at a particular disadvantage in climbing the socioeconomic ladder because they are 2.6 times more likely than whites to have spent most of their childhood in a nontraditional family structure, the researchers found. African American children are six times as likely as whites to be raised in a mother-headed family, 2.7 times as likely to be raised in a stepfather-headed family, and twice as likely to be raised in a nontraditional father-headed family.

But the socioeconomic disadvantages that African Americans experience cannot be explained entirely by the higher incidence of alternative families in the African American population. African American men from every family structure and every family SEI level averaged 6 SEI points lower than their white counterparts.

While single-mother homes were not damaging to most respondents' future prospects, the USC-UW researchers report that such homes can have dire consequences for certain groups of children. Respondents reporting a family head with no occupation were themselves 2.4 times more likely to work in the lowest occupational stratum than were respondents from families whose head of household worked. Men from female-headed households were more than 10 times as likely to report no occupation for the head of their childhood household.

"Compared with children from traditional two-parent homes, children being raised by non-working single moms are thus at much greater risk for perpetuating their impoverished backgrounds as adults," Biblarz said. "But to ensure better socioeconomic outcomes for these children, it would be far more useful to focus on the mother's employment status than her marital status."