White Americans are becoming a minority in an increasing number of parts of the U.S. Koichi Kamoshida/Getty Images

It isn’t exactly a secret: White Americans are declining as a percentage of the whole. But, while some predictions say whites are on track to be a minority in the United States in the next 30 years, an analysis released Thursday of census figures found that the non-Hispanic white population has already dropped below 50 percent in hundreds of counties across the nation.

All told, there are 370 counties in 36 states plus the District of Columbia where that is the case, making up 12 percent of counties. But because those counties are so populous, they represent nearly one-third of the total U.S. population, according to the Wall Street Journal. Thirty-one counties were added to the list since 2010.

There are some stark differences between generations when it comes to the racial divide. Three-quarters of Americans over the age of 55 are white. Of those who roughly fall into the millennial category (18 -34-year-olds), 56 percent were white. When you drop to the lowest age group — 5 and under — white children do not account for a plurality.

A woman drives past a sign in the Koreatown neighborhood of Los Angeles in 2014. In much of Southern California, non-Hispanic white Americans no longer account for more than 50 percent of the population. Reuters

As minority populations boom, white Americans are seeing a noticeable decline in numbers. The group is the only one with a higher death rate than birthrate. In 46 states, the population of white Americans under the age of 20 declined. Hawaii, Utah, South Dakota, North Dakota and D.C. were the only states or areas that did not see that trend.

“I don’t think people fully appreciate how much natural increase [more births than deaths] contributes to the nation’s growing diversity,” Kenneth Johnson, a demographic researcher at the University of New Hampshire’s Carsey School of Public Policy, said last year. “If you ask people why is America more diverse, they would say it’s because minorities are being born. What nobody ever thinks about is that a lot more whites are dying.”

Minority populations, on the other hand, account for roughly 95 percent of U.S. population increase, mostly as a result of high rates of Asian and Hispanic births.