More white people died in the U.S. last year than were born, a surprising slump coming more than a decade before the census predicts that the ranks of white Americans will drop with every passing year.

Population estimates for 2012 released by the Census Bureau Thursday showed what’s known as a natural decrease — a straightforward calculation of births minus deaths — of about 12,400 people among the nation’s 198 million whites who are not Hispanic. Overall in Maine, the number of deaths exceeded births statewide in 2012.

Though the percentage is small, several demographers said they are not aware of another time in U.S. history — not even during the Depression or wartime — when the dominant racial group experienced such shrinkage. No other group showed a similar fall off.

The decrease was offset by 188,000 white immigrants, primarily from Canada and Germany, but also from Russia and Saudi Arabia. And non-Hispanic whites remain the single largest group, making up 63 percent of the country.

But demographers were surprised by the outsized drop in births compared to deaths, which the Census Bureau projects will begin happening with regularity by 2025.

“We’re jumping the gun on a long, slow decline of our white population, which is going to characterize this century,” said William Frey, a demographer with the Brookings Institution. “It’s a bookend from the last century, when whites heped us grow. Now it’s minorities who are going to make the contributions to our economic and population growth over the next 50 years.”

A number of demographic and economic factors are behind the slowdown that has been underway for several years.

As a group, non-Hispanic whites are considerably older than anyone else, with a median age of 42. The median age for Asians is 34. For African Americans, it’s under 32 and for Hispanics it’s under 28.

Women with college degrees of all races have been delaying marriage and childbearing to the end of their 20s and beyond, until they have finished their educations and established careers. Once they settle down, they tend to have fewer children. Census figures also show that white women are far more likely to be childless than Hispanic or African American women.

The recession that began in late 2007 exacerbated those longterm trends. Fertility rates have been slowly dropping since 2007. For white women, they are now below the level considered necessary to keep the population at a stable level. During the recession, researchers found women who had lost health insurance or whose partners were unemployed were reluctant to have more children at a time when they could least afford them.

This latest demographic fall is not the first harbinger of the future. Earlier this year, census figures showed that for the first time in U.S. history, a majority of newborn babies were minorities.

Ken Johnson, a demographer with the Carsey Institute at the University of New Hampshire, said the demographics suggest many people are making the decision about whether to have children as if the recession had not ended. Even if the fertility rates pick up, he said, there will be just a temporary lull before people born in the 1940s and 1950s start dying in large numbers.

“This has more to do with births than it does deaths,” he said. “Once this recession has waned, we’re probably going to see at least a temporary uptick in births, until death rates start to rise. Then there’ll be no stopping it.”

The decline in the non-Hispanic white population has happened more quickly than demographers with the Census Bureau have been predicting. That’s because both births and immigration levels, which can counter the drop, have slowed more than expected in recent years, said Jennifer Ortman, a demographer in the population projections division of the Census Bureau.

Census demographers expect the growth rate for non-Hispanic whites to resume going up, slowly, when the economy improves. Whites should peak in 2024, when the oldest baby boomers, who are overwhelmingly non-Hispanic whites, are well into their 70s and dying in larger numbers. After falling just short of 200 million every year.

The decrease for whites has little significance in the short term, said Dowell Myers, a demographer and urban planner who teaches at the University of Southern California.

“In California, we roll our eyes at this,” he said. “Whites have been a minority here since 1999. But whites are still a majority of voters. Babies don’t vote. Older people vote. So it doesn’t have any direct functional meaning.”

But Frey, the Brookings demographer, said the natural decrease in whites suggests the U.S. will need immigration to continue if it is going to thrive.

“It’s going to be clear soon, if it isn’t already, that we’re going to depend much more on our young, largely minority popoulation to keep not only the economy of the country going, but the well-being of our aging white population,” he said. Last year we saw the majority of babies are minorities. Now we see more whites are dying than being born. Together, that tells us a lot about where we’re going as a country.”