While most recent discussion about the country’s changes has focused on ethnicity or race, there are some other frames for seeing the alterations in our national portrait.

How we behave, who we are. What the rules are.

For instance, nestled within the massive data trove constantly being collected and collated and published by the U.S. Census Bureau was this radioactive nugget about the nation's young adults:

— In 1975, 71 percent of Americans aged 30 were married, had a child and were out there in the real world, that is living away from their parents. Nearly three in four.

— In 2015, the comparable figure was just 32 percent. Less than one-third.

Leaving aside all the other ways in which the country has morphed, just those numbers imply different economies, different social expectations, different trajectories for tax collection and social services.

Thirty-year-olds are, after all, right in the middle of that millennial bulge — part of the largest number of people in the workforce.

The breakdown is striking in several ways.

The share of these young adults people who have been married has fallen from 89 percent to 57 percent. The share that is living with a child has plummeted from 76 percent to 47 percent.

So you think we're a different country now than we used to be? Well, as the actor Jeremy Irons compellingly put it in two movies — one about a killing, one an animated favorite from Disney:

"You Have No Idea."