The number of American women who are raising children without a husband present grew by more than 25 percent during the 1990s, according to data released today from the 2000 census.
The census in April counted nearly 7.6 million households headed by women with children younger than 18 at home, but no husband. There were just over 6 million in 1990.
The 10-year rate of increase was nearly twice the 13 percent growth of the U.S. population as a whole.
"That is definitely a huge trend, and it is worldwide," said sociologist Steven P. Martin of the University of Maryland, College Park. "Nonmarital childbearing is occurring in increasing numbers in just about any developed country you look at."
In the United States, the trend is strongest among minority groups, "but it is rising very rapidly among poor whites as well," Martin said.
The economic and social consequences are serious, he said: "Across the board, children and mothers in nonmarital birth families do much worse than the children of married parents."
At the same time, the new census data also show that more and more younger Americans are delaying marriage and living alone, or cohabiting with their partners without getting married.
Older Americans were slightly less likely to be living alone in 2000 than a decade ago. "It looks like married couples are surviving longer together," Martin said.
The new data are reported in the "Profile of Demographic Characteristics for the United States." State-by-state details are to be released beginning Friday.
Among the key findings:
The median age of people in the United States reached 35.3 in 2000 - the oldest in the nation's history. In 1990, the median age was 32.9. In 1890, it was 22.
The aging of America in recent decades has been the result mostly of the graying of the huge post-World War II "baby boom" generation.
Born between 1946 and 1964, and once the definers of America's "youth culture," all 81 million boomers are now older than the nation's median age - between 36 and 54 on Census Day last year.
Now they are approaching eligibility for early retirement. But sociologists studying the potential retirement boom say it might be more gradual than expected.
Since the mid-1980s, growing numbers of older people have been working past retirement age, said Joseph F. Quinn, professor of economics at Boston College.
Changes in Social Security, pension and 401(k) plans that reduced penalties for working too long will mean more baby boomers, too, are likely to continue working, at least part time, well into their 60s and 70s.
"Not everyone's goal is to stop working and fish," Quinn said.
Growth in the elderly population - those 65 and older - was the slowest in history during the 1990s, up just 3.7 percent to 35 million in 2000. That is attributed to the slump in birthrates during the Depression, in 1929 and the 1930s.
Even so, the 85-and-older crowd was one of the fastest-growing in the United States, up 37.6 percent since 1990 to 4.2 million, thanks to improved medical care.
The ratio of men to women in the United States also improved for the first time since 1910, rising from 95.1 men for every 100 women in 1990, to 96.3 last year.
Martin credited both increased immigration, which is lopsidedly male, and greater improvements in life expectancy for men, relative to those for women.
The percentage of homes that are owner-occupied increased during the 1990s, from 64.2 percent in 1990 to 66.2 percent last year. Housing vacancy rates, meanwhile, declined.
4 million people - one in every 70 in the United States - were institutionalized in April 2000. That includes those confined to prisons, hospitals, nursing homes and rehabilitation centers. The total grew by 21.7 percent since 1990.
They now outnumber the 3.7 million living in noninstitutional group quarters, such as college dorms, barracks, shelters and halfway houses.
Although the largest number of people who described themselves as Hispanic were Mexicans (20.6 million, up 53 percent during the 1990s), the fastest-growing category of Hispanics were those counted as "others," including those with roots in Central and South America, the Dominican Republic and Spain. They numbered nearly 10 million last year, almost twice the count in 1990.
The fastest-growing segment of the Asian population in America was those with roots in India. Their numbers more than doubled during the 1990s, to 1.7 million.
The number of Japanese counted in the 2000 census declined 6 percent, to less than 800,000. Demographers say that the Japanese were early immigrants to the United States and that immigration in recent decades has been slight.
"Large numbers of Japanese are old enough that death is affecting the demographics," said Martin.
Of all the groups counted by the 2000 census, one of the slowest-growing was the traditional family - a married couple living with their own children under 18.
The census counted 24.8 million such households, up just 5.5 percent since 1990 - less than half the growth rate of the United States as a whole.
In 2000, they constituted 23.5 percent of all U.S. households, down from 44 percent in the 1960 census, according to the Population Reference Bureau.
Women raising their children without a husband present, meanwhile, constituted 7.2 percent of the total households in the country last year. But their numbers grew 25 percent during the 1990s, from 6 million to 7.6 million.
Part of the explanation seems to be a weakening of the influence of social or moral strictures against out-of-wedlock births.
In surveys in most developed nations, Martin said, sociologists have found an increasing percentage of women who say they can imagine themselves having children out of wedlock.
Sociologists still debate whether U.S. social welfare programs that helped support unmarried mothers and their children also contributed to that perception, Martin said.
In recent years, however, "welfare to work" programs have sharply limited such assistance. "And for whatever reason," he said, "nonmarital birth rates have leveled off within the last five years."
The 2000 census also found strong growth among a variety of nonfamily households, a trend launched in the 1960s.
To the Census Bureau, a "family" consists of two or more people living together who are related by blood, marriage or adoption. "Nonfamilies" include people living alone or with one or more unrelated people.
Most American households in 2000 - about 71.8 million of them, or 68 percent - continued to qualify as families. Their growth was about 11 percent - close to the 13 percent increase in the nation's population as a whole.
But the number of nonfamily households grew twice as fast during the 1990s - by 23 percent. Studies suggest that a major component of that growth is the increasing number of young people, ages 18 to 29, who are staying single, Martin said.
"People used to be worried, in the '70s and '80s, when they started delaying marriage, that there would be no marriages at all," he said. Instead, "we are seeing lots of later marriages."
Late marriages can mean fewer births. But unlike many other developed nations, he said, "fertility in the U.S. seems to be staying surprisingly high. A lot more women are having births in their 30s."
Researchers aren't sure just why America's young people are delaying marriage.
Some say it's related to poor earnings among men in their early 20s, making them temporarily less "marriageable" in their own eyes and those of potential spouses.
Another factor, Martin said, might be the increasing importance of jobs and careers in the lives of young women. He speculated that men might have begun looking for women with good earnings. If so, he said, "younger women may feel less pressure to marry right away."
Increasing college attendance might be delaying marriage. And many young people are opting for cohabitation instead of marriage.
The number of "unmarried partners" - unrelated people with "close personal relationships" who are sharing a household - was up almost 72 percent during the 1990s, from 3.2 million in 1990 to 5.5 million last year.