I can remember when my parents celebrated their 25th wedding anniversary — I was a pimply and obnoxious 15-year-old at the time — and I’m a little awed to realize I’ll be celebrating my own silver anniversary in just another four years.

But the census is telling us such events are increasingly rare:

More than half the Americans who might have celebrated their 25th wedding anniversaries since 2000 were either divorced, separated or widowed, according to a census survey released today.

For the first time at least since World War II, married people had a less than even chance of still being married 25 years later.

The latest survey by the Census Bureau confirmed that most Americans eventually marry, but they are marrying later and are less likely to be wed only once. Those trends continued, although the proportion who have ever been divorced, about one in five, remained constant.

“Basically, it looks like we’re pretty much holding steady,” said Rose Kreieder, a Census Bureau demographer. “There are not radical differences.”

Among people in their late 20s, a majority of men — 54 percent — had never married, as had 41 percent of women. In 1996, the comparable proportions were 49 percent among men and 35 percent among women.

At that time, about 69 percent of men and 76 percent of women age 15 and older had married only once. In the latest analysis, 54 percent of men and 58 percent of women had married only once.

The oldest baby boomers recorded the highest divorce rates. Among people in their fifties, 38 percent of men and 41 percent of women had been divorced. In 1996, the comparable figures were 36 percent and 35 percent.

One statistical constant has been the so-called seven-year itch, as popularized in the play and film about errant husbands. Couples who separate do so, on average, after seven years and divorce after eight. The duration of first marriages that end in divorce appears to have increased slightly among men.