The first race and ethnicity breakdowns from the 2020 Census, released Thursday, show a more diverse population than ever in the nation’s history.

The report marks the first time the absolute number of people who identify as White alone has shrunk since a census started being taken in 1790. The number of people identifying as non-Hispanic White and no other race dropped by 5.1 million people, to 191.7 million, a decrease of 2.6 percent.

The country also passed two more milestones on its way to becoming a majority-minority society in the coming decades: For the first time, the portion of White people dipped below 60 percent, slipping from 63.7 percent in 2010 to 57.8 percent in 2020. And the under-18 population is now majority people of color, at 52.7 percent.

The new data shows how the ethnic, racial and voting-age makeup of neighborhoods shifted over the past decade, based on the national house-to-house canvass last year. It is the data most state legislatures and local governments use to redraw political districts for the next 10 years.

It indicates that the country is “much more multiracial and much more racially and ethnically diverse than what we measured in the past,” said Nicholas Jones, director and senior adviser of race and ethnic research and outreach at the Census Bureau’s population division.

The opioid epidemic and lower-than-anticipated birthrates among millennials after the Great Recession accelerated the White population’s decline, said William Frey, a demographer at the Brookings Institution.

“Twenty years ago if you told people this was going to be the case, they wouldn’t have believed you,” he said of the White decline. “The country is changing dramatically.”

In April, 2020 Census state population totals showed the country grew by just 7.4 percent in the past decade, more slowly than any decade except the 1930s. The states with the most growth were in the West and the South, which have seen an influx of people moving in from other countries and other states.

The largest and most steady gains were among Hispanics, who doubled their population share over the past three decades to 62.1 million people, or 18.7 percent, in 2020 and who are believed to account for half of the nation’s growth since 2010.

Asian people, who made up about 3 percent of the population in 1990, also doubled their share since then, to 6.1 percent, while the Black population’s share held steady at 12.1 percent.

Six states and the District of Columbia now have majorities of people of color, including Nevada and Maryland, which passed that milestone in the past decade. Maryland is now 47.2 percent White, and Nevada is 45.9 percent White. White population fell in three-quarters of counties, and in 35 states.

The diversification of the nation is projected to continue, with Whites falling below 50 percent nationally around 2045, Frey said, adding that, at that point, there will be no racial majority in the country. Between 2015 and 2060, the Hispanic and Asian populations are expected to approximately double in size, and the multiracial population could triple due to immigration and births.

The number of people who identify as multiracial has changed considerably since 2010. It was measured at 9 million people in 2010 and was 33.8 million in 2020, a 276 percent increase.

That could make redistricting more complex, said Kimball Brace, president of Election Data Services, a political consulting firm specializing in the analysis and presentation of census and political data.

“We’re seeing so much more of this ‘two or more races’ … and that increase is significant because it will start muddying the waters a bit when we get to the question of drawing districts and the creation of different minority seats, and will it be an African American or a Hispanic seat? Because things are starting to merge together," he said.

Some of the changes may be due not only to actual increased diversity but also to changes in how people self-identify. The bureau’s design, data processing and coding procedures have made it easier for respondents to identify as more than one race.

“It looks like most of the increase in the diversity index is because the current census worked hard to identify diversity that was already there, but it will be some time before we know for sure,” said Steven Martin, a senior demographer at the Urban Institute.

Rogelio Saenz, a University of Texas at San Antonio demographer and sociologist, said the multiracial population is even younger than the Latino population — he estimated 19 or 20 years old — which means that segment of the population is only expected to grow as more multiracial people reach childbearing years. Interracial marriages also have been increasing across the United States, and in general he said more people are conscious and aware of their heritage, therefore likely to check another “race” box on the census.

“There’s a greater degree of appreciation for the multicultural, multiracial roots that people have and I think that’ll continue to be the case,” he said.

The shifts signal what Frey calls a “cultural generation gap,” with older generations that are much Whiter than younger ones. Racial minorities will drive all the growth in the U.S. labor force as White baby boomers retire and will make the difference between growth and decline in rural and suburban areas. The year 2011 was the first time more non-White babies were born than White babies, and for the past two decades, the growth of the nation’s child population has been due entirely to Hispanic, Asian and multiracial people.

Their needs will be juxtaposed against — and in some cases seen as competing with — the needs of older generations: for example, public spending on senior services vs. schools or English-language classes or job training.

Arturo Vargas, chief executive of the NALEO Educational Fund, a Latino advocacy group, said the numbers for Hispanics were “lower than expected, but not a surprise because the initial apportionment numbers in April were lower than we expected."

Nevertheless, “it is extraordinary that Latinos accounted for more than 50 percent of growth for the total U.S. population,” he said. "That more than one out of two new Americans is a Latino speaks volumes about the policies and decisions leaders need to make to ensure a strong America of the future. We need investments in Latino children. The children in our classrooms today are our future doctors and lawyers and political leaders.”

The new data showed that large counties — those with over 50,000 residents — are growing the most, while smaller counties have shrunk. The U.S. population is increasingly metropolitan, with metro areas growing by 8.7 percent.

All 10 of the country’s most populous cities grew in the past decade, with Phoenix overtaking Philadelphia in the No. 5 slot. The top four are New York City, Los Angeles, Chicago and Houston.

The data release comes amid concerns over the census’s accuracy. The 2020 count was beset by problems, including insufficient funding for preparation, Trump administration attempts to add a citizenship question and block undocumented immigrants from being counted for apportionment, and the coronavirus pandemic, which caused major delays for the survey. Some census-takers said they were pushed by their superiors to bend rules to close out their caseloads more quickly, and experts worried that Hispanics in particular might be reluctant to respond to the survey.

But Thursday’s data release was largely in line with earlier estimates.

“The data we are releasing today meet our high data quality standards,” Ron Jarmin, the bureau’s acting director, said Thursday.

Thomas Saenz, president and general counsel of the Mexican American Legal Defense and Educational Fund, said the initial data was on track with earlier estimates for the Hispanic population.

“I’m certain there was an undercount; there always is … but in comparison to what might have been, they don’t look bad,” he said of the numbers.

Further analysis is needed to determine the accuracy, he said, adding, “The Census Bureau still has a lot of work to do to undo the damage presented by the politicization of the census, but looking at the numbers today, it did not have the effect that Donald Trump and others intended.”

Brittany Renee Mayes, Silvia Foster-Frau and Meghan Hoyer contributed to this report. This story will be updated.