White, non-Hispanic kids will no longer make up the majority of America's youth in just five to six years, according to Census Bureau projections released Wednesday.

Those projections, which include four different scenarios for population growth, estimate that today's minority ethnic groups will soon account for at least half of the under-18 population, either in 2018 or 2019.

"This is going to start from the bottom of the age distribution and move its way up," said William Frey, demographer and senior fellow for the Brookings Institution. "All of these projections show we're moving to greater diversity in the United States."

Already, more than half of American babies being born belong to racial and ethnic groups traditionally thought of as "minorities" -- which means it could soon be time to toss that word out completely.

By the time those kids grow up to become adults -- sometime between 2036 and 2042 -- everyone in the working-age population (ages 18 to 64) will be a member of a group that comes up short of the 50% line.

Demographers call it a "minority-majority." No one single racial or ethnic group will make up more than half of the population.

White, non-Hispanic people currently make up about 63% of the entire United States population. Starting in 2041, they'll account for less than half, according to projections.

The Census Bureau said international migration will eventually surpass births, becoming the single largest driver of population growth by 2050. Births have been the main catalyst for U.S. population growth since at least 1850, when the Census Bureau started gathering the information.

"Our nation has had higher immigration rates in the past, particularly during the great waves of the late 19th and early 20th centuries," Thomas Mesenbourg, Census Bureau senior adviser, said in a written statement. "This projected milestone reflects the mix of our nation's declining fertility rates, the aging of the baby boomer population and continued immigration."

Related: I'm a minority and a Silicon Valley 'trade secret'

Meanwhile, as the population ages and lifespans grow longer, the share of America's population that's of working age is on the decline. As of last year, people ages 18 to 64 accounted for roughly 63% of the U.S. population, but by 2060, their share could fall to 57%. Unless the retirement age also rises, that could cause a big problem for funding entitlement programs like Social Security and Medicare.

Read the full Census report here.