Something unusual happened in 2018: Americans turned out to vote.

Granted, that’s a statement that earns its power mostly as a relative comparison. Turnout was over 50 percent — a lot for a midterm, not a lot for a presidential year and fairly low compared to many other democracies. But because more voting is generally seen as better than less voting, higher-than-normal midterm turnout didn’t prompt many complaints.

On Tuesday, the Census Bureau released data that showed even young people turned out to vote more heavily than in past midterms. Young people, perennially the subject of “why don’t young people vote” stories, turned out at nearly twice the rate they had in 2014, helping to boost turnout overall.

The pattern in turnout by age is interesting. It’s generally a fairly smooth curve, from low turnout among young people to higher turnout among older people, until the dispassionate passage of time begins reducing turnout rates for other reasons.

There are a lot of reasons for this, including that younger people move more often (meaning they need to re-register to vote), that they tend to have less stable employment (and can’t as easily get to the polls) and that voting is a habit that’s built over time. I know this because I have read a lot of “why don’t young people vote” articles.

But the graph above, which we published Tuesday, makes clear how wide the gulf is in voting habits by age. Only about a quarter of people under 20 voted in 2018, in this year where the youth vote surged. That’s not really all that impressive.

Someone on social media wondered how the turnout rates above correlated to population. As it turns out, it’s an interesting thing to consider.

The voting data from the Census Bureau includes estimates of how many citizens there are of every age in the United States. That allows us to create the graph below, showing how many citizens in each age group voted — and how many didn’t.

It’s fairly consistent that there are about 4 million citizens who are at every age from 18 to 60. In 2018, fewer than a million of those 18-year-olds cast a ballot, but 2.5 million of those 60-year-olds did.

That’s just among citizens old enough to vote, of course. If we consider all U.S. residents at every age, the number of people voting is a much smaller subset — one heavily weighted toward older Americans. (The most recent single-year-of-age data from the Census Bureau is from 2017, but the differences are probably minimal.)

Notice, too, that including noncitizens increases the number of younger Americans who didn’t cast a ballot in 2018.

It’s not earth-shattering to note that a small group of U.S. voters makes decisions for the population as a whole. But it’s still worth remembering, in light of the surge in turnout last year, that a slightly bigger small group is still a small group.