The median age in the U.S. reaches a record high, approaching 40 years old

America is red, white, blue ... and gray. The median age in the U.S. reached a record high last year, rising to 38.9 years, and it's likely only going up from here, per Census Bureau data out Thursday.

Why it matters: Decades of lower birth rates and increasing (until recently) life expectancy means older folks make up an ever larger share of the population.

• Put another way: The baby boomers and their kids — the millennials or echo boomers — are aging the country. Call it the OK, (echo) boomer era.
• This has all kinds of implications for the economy, particularly in the workforce where the aging population is keeping the labor market tight.
• The aging workforce could drive worker shortages for years to come — especially in health care, which will become even more crucial as we gray.

By the numbers: 17 states have a median age above 40.

• Maine has the highest median age in the country at 44.8.
• Utah, which has a relatively high fertility rate, is the youngest state with a median age of 31.9.
• In 1980, the median age was 30.

What they're saying: "As the nation’s median age creeps closer to 40, you can really see how the aging of Baby Boomers, and now their children — sometimes called echo boomers — is impacting the median age," Kristie Wilder, a demographer in the Census Bureau’s Population Division, said in a statement.

• "Without a rapidly growing young population, the U.S. median age will likely continue its slow but steady rise.”

Zoom out: The U.S. is still a younger country than its European peers, as the New York Times points out. "Immigration has historically kept the United States young," writes Dana Goldstein.

• But immigration has slowed in recent years.