Newly-released census data show that among people in their late twenties, a higher proportion of people have never been married.
In 1986, the first year that marriage data was collected by the Survey of Income and Program Participation, 73 percent of people between the ages of 25 and 29 had been married at some point. As of 2009, that number is at 53 percent; new numbers were last released in 2001.
The reasons are what you'd might guess—later marriage, greater societal acceptance of couples living together without being married. But none of this means that we need to mourn (or celebrate) the death of marriage as an institution; the data also indicate that people who are married stay together longer than they did in the mid-eighties. Per the Washington Post:
Three in four couples who married after 1990 celebrated a 10-year anniversary, according to census statistics reported Wednesday. That was a rise of three percentage points compared with couples who married in the early 1980s, when the nation's divorce rate was at its highest.
The sociologists interviewed by the Post specifically point to later marriage and more-educated women (helpful stat: "In 2009, 31 percent of brides had a college degree, up from 21 percent in 1996") as being connected to these more stable marriages. It stands to reason, conservative handwringing aside, that people who enter into marriage when they have more personal and financial stability are more likely to have the inner and outer resources, and the motivation, to make it work.
Apart from education, there was variance when it came to race and ethnicity:
Census demographers noted that the percentage of never-married black women 55 and older rose to 13 percent in 2009. The magnitude of the change suggests that many more black women than white women will never marry, the report said...The census also showed that a higher proportion of people who have married recently are Hispanic, which is the fastest-growing minority group in the country.
The divorce rate for black women is also higher than for white, Asian, or Hispanic women, the study found, with half of first marriages ending in divorce.