A new Census Bureau report shows the baby-boom generation fading further into the gray and giving way to millennials in a country whose younger generations are also becoming more diverse.

The white population in the United States reached an all-time high median age of 43, while those younger than 5 were outnumbered by minority children.

“That’s a reflection of how the U.S. is aging,” said Mark Hugo Lopez, director of Hispanic research at the Pew Research Center.

At the same time, the latest census data reflect earlier findings that China has replaced Mexico as the chief source of U.S. immigrants. Hispanic immigration has slowed overall as Asian migration chugs along.

“At the national level, a lot of these trends we see now tend to be continuations of older trends,” said Ben Bolender, chief of the Census Bureau’s population estimates branch.

The annual update of population estimates released Thursday includes changes by age, sex, race and Hispanic origin nationwide and by states and counties between April 1, 2010, and July 1, 2014. Although the report is short on dramatic shifts, it offers a snapshot of further changes in long-term trends, especially as the nation becomes more diverse.

“In a sense, 2015 marks the demographic passing of the baby-boom generation, and it will continue to be an ever-smaller part of the total U.S. population until it disappears altogether later this century,” said
C. Matthew Snipp, a sociology professor at Stanford University. The question now, he said, is whether the rise of the millennial generation will produce the same cultural revolution attributed to boomers.

William H. Frey, a senior fellow at the Brookings Institution and the author of “Diversity Explosion: How New Racial Demographics Are Remaking America,” said the report shows the white population is growing older and shrinking in proportion to minority groups, with whites experiencing a higher number of deaths than births. Non-Hispanic, single-race whites were the only group for which deaths exceeded births between 2013 and 2014. Minority children younger than 5 now make up 50.2 percent of that population group, the report found.

“This year is the first time the 0-to-4 population is minority-majority,” Bolender said.

It was a shift long expected: In 2013, the rate was close enough — about 50-50 — that young minority children were on the cusp of outnumbering white children.

Nevada moved closer to becoming a minority-majority state — where minorities make up more than 50 percent of the population — joining a club including Hawaii (77 percent), California (61.5 percent), New Mexico (61.1 percent) and Texas (56.6 percent).

Bolender said the data also reflect a shift in patterns. Immigration from China and other Asian countries has gradually increased while Mexican immigration, which began slowing in 2004, fell sharply in the Great Recession.

The 2013 American Community Survey found that the United States received 1,201,000 immigrants, with China the top sending country at 147,000. Immigrants from India numbered 129,000, compared with Mexico’s 125,000 — a difference that was not statistically significant.

In the Washington area, the proportion of black and multiracial black people has remained steady, at about 27.8 percent, since around 2000, Bolender said. But within the District, the proportion has been declining. In 2000, the District was about 62 percent black or black in combination. By 2010, that number dropped to 53 percent. Today, it’s 50.6 percent.

“So if those trends were to continue, we would expect that to drop below 50 percent in the next few years,” Bolender said.

The report also showed that the District experienced an increase in the percentage of its under-20 white population. At the same time, the nationwide under-20 population is 52.2 percent white. Thirteen states now have minority-majority under-20 populations, up from five in 2000, Frey said. None showed an increase in the under-20 white population.

While the Census Bureau report groups the District with states, many demographers say that the most apt comparison is with other U.S. cities.