Don’t stock up on silver anniversary cards. More than half the Americans who might have celebrated their 25th wedding anniversaries in the year 2000 were either divorced, separated or widowed, according to a census survey released Wednesday.

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

The latest survey by the Census Bureau, using 2004 data, confirmed that most Americans eventually marry, but they do so later and are less likely to be wed only once.

The oldest baby boomers recorded the highest divorce rates. Among people in their 50s, 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. Couples who separate do so, on average, after seven years and divorce after eight.