(Newsroom America) -- Young adults are increasingly marrying at later ages, if at all, and giving birth to more children outside of marriage, a new Population Reference Bureau (PRB) report finds.
As a result, more Americans are living in cohabiting-couple households, single-parent families, or alone, while households containing married couples with children are in sharp decline, according to "Household Change in the United States," an analysis based on decennial census and Current Population Survey data.
"Married-couple families with children–once the predominant household structure—now are even outnumbered by one-person households," said Linda A. Jacobsen, vice president of Domestic Programs at PRB and co-author of the report.
In 2010, only 20 percent of all households included married couples with children, down from a high of 44 percent in 1960. By contrast, people living alone now represent 27 percent of all households.
For the first time, households made up of married couples with and without children dropped below 50 percent of all households, Jacobsen noted. At the peak in 1960, married couples represented 75 percent of all households.
* By 2012, only 46 percent of young adults ages 25 to 34 were married, down from 55 percent in 2000. The median age at first marriage continues to rise, reaching 28.1 for men and 26.5 for women in 2011.
* Married couples and unmarried cohabiting couples are equally likely to have children younger than age 18 in their home, about 40 percent for each group.
* In 2010, 41 percent of all births were to unmarried parents, up from 33 percent in 2000. The steepest increases in nonmarital births were among women in their 20s: About 63 percent of births to women ages 20 to 24 occurred outside of marriage in 2010.
* Not only are women having fewer children (the current U.S. average is 1.9 children per woman), but rates of childlessness also have increased. Between 1980 and 2010, the share of women ages 40 to 44 who were childless nearly doubled, increasing from 10 percent to 19 percent.
"If current trends continue, more men and women will postpone marriage until their 30s, thus spending a smaller portion of their adult lives married," said Mark Mather, associate vice president of Domestic Programs at PRB and report co-author. "Compared to their mothers and grandmothers, more of today's 25-year-olds appear on track to remain unmarried through age 40."
Because marriage rates have declined faster and unmarried childbearing is highest among people without college degrees, more children are at risk of growing up poor, according to Mather.
"Although about half of nonmarital births are to cohabiting couples, these unions tend to have fewer economic resources and be less stable than marriages."
Declines in fertility and increases in divorce and nonmarital childbearing may also reduce the number of children who are available and willing to care for an aging parent, especially if that parent wasn't around when his or her children were growing up, Jacobsen said.
The Population Reference Bureau informs people around the world about population, health, and the environment, and empowers them to use that information to improve the well-being of current and future generations.
The full report is available at www.prb.org and data on household types are now available for all U.S. states and counties in PRB's DataFinder.