Did you know that in 1970 married couples with children made up 40 percent of American households? Today, they comprise just 20 percent (see figure). 

 What looks like a dramatic drop in married households may be more of a change in when, and in what order, adults experience certain life events. In other words, a family postponed is not necessarily a family forgone.

 During the 1970s, younger baby boomers were still children living at home. Because boomers were the largest generation in U.S. history, they left a lasting footprint on the makeup of households and family life.

 As those children grew up and moved out, we saw an increase in people living alone while also seeing a decline in households with married parents. Over the last 40 years, the share of adults living alone grew by a third for women. It more than doubled for men.

 These trends also mirror the rising age at marriage, which has climbed by 5 years for men and women since 1970. Whereas previous generations may have lived at home until they married in their early 20s, not only are adults getting married at an older age but they now are often living on their own before tying the knot.

Childbearing is an important part of the equation too. Just as adults are waiting longer to marry, they are also delaying having children. The average age when women give birth to their first child has risen from 21 to 25 [PDF <1.0 MB] since 1970. This helps explain why the share of households made up of married parents has fallen so dramatically while that of married couples without children has not.

To find out more about the composition of modern American families, check out a new report released today: