A woman walks out of a polling place after voting in the 2016 Nevada primary election in Las Vegas. (John Locher/AP)

This graph, created by Pew Research Center, is striking.

(Pew Research Center)

That surge from the 2014 midterms to those of 2018 is remarkable, pushing the number of voters who are Generation X, millennial or the as-yet-unnamed-generation-that-is-commonly-and-somewhat-lazily-referred-to-as-Generation-Z past voters who are baby boomers or older. It’s the first time this has happened in a midterm election, and a surge in younger voters is the central factor.

But then you stop and look at the chart again. You think about what it’s telling you and what it shows. And suddenly it doesn’t really seem very remarkable at all.

First, this isn’t the first election in which X-through-Z voters outnumbered boomer-and-older voters. That happened in 2016 as well, as Pew notes. Second, those lines seem to show that 2014 was as much of an outlier as 2018, breaking the steady upward trend of X-through-Z voters. Put 2014 turnout at around 45 million or so, in line with the trend, and 2018 seems less shocking.

There’s also another important point that we tend to obscure. Why is that line trending up while the boomer-plus line drops? Because that’s how population works. We like to think about “millennials” as “young people,” but according to Pew’s definition of the age group, some millennials are turning 38 this year. That’s not generally what we think of when we think of millennials.

Millennials are getting older as boomers and members of the “silent generation” are, lamentably, dying off. Census Bureau data shows how each generational group has changed from 2010 to 2017. Since 2010, the number of people in the silent generation has fallen by 30 percent while the number of people in Generation Z has increased by 50 percent. (How did the number of millennials increase despite members of that generation being born no later than 1996? Immigration.)

(Philip Bump/The Washington Post)

If we combine these categories, we see how the shift shown in that first graph from Pew was inevitable. In 2010, there were about as many boomers and silent generation members as X-through-Z members who were 18 or older. By 2017, there were nearly 50 percent more members of the younger generation over the age of 18.

(Philip Bump/The Washington Post)

So why didn’t they outnumber older voters at the polls sooner? Because younger people vote much less consistently than older ones. Here’s what turnout has looked like by age in the past three federal elections.

(Philip Bump/The Washington Post)

There’s an important, broader point worth making here, too. The definitions of the various generations used above are not objective delineations. They are, instead, where Pew has decided to draw the lines. From a demographic standpoint, only the boomers are a clearly defined generation according to an expert I spoke with several years ago. All of the other “generations” are mostly marketing delineations.

In other words, there’s not anything particularly significant about the fact that X-through-Z is now outvoting boomers-plus. It’s basically the same as saying that those born in 1964 or earlier made up less of the vote in 2018 than those born from 1965 on. Or, put another way, that those age 54 or older cast fewer votes than those 53 or younger.

This ... isn’t that surprising. Census Bureau data show that, since 2000, the age at which more people who are younger outvoted those who are older has ranged from 47 to 55. In other words, in 2000, more people age 47 or younger voted than people 48 and up.

(Philip Bump/The Washington Post)

In 2018, the age was 53. That Pew’s generational delineations prompt it to look at 54 is, essentially, a quirk.

(You can also see here how the same effect was in play in 2016. The crossover age there was 51 — when the youngest boomers were 52.)

None of this is meant to disparage the Pew Research Center, which does consistently good work. It’s just to point out that the generational benchmark being noted isn’t really all that notable.