There’s an odd dynamic at play in Facebook chief executive Mark Zuckerberg’s appearance on Tuesday before members of the U.S. Senate on Capitol Hill. Each of those senators is making decisions for a pool of constituents ranging from about 623,000 (Vermont) to 39.5 million (California).

Zuckerberg’s constituency is probably about two-thirds of the country.

If we aren’t comparing apples and oranges here, we’re at least comparing apples with, say, apple Jolly Ranchers. A senator’s constituency is easily defined — residents of his or her state — while Zuckerberg’s is more nebulous. The company uses two metrics, generally: daily active users and monthly active users, the difference being (obviously) how often people access the site.

In the fourth quarter of 2017, about 184 million people in the United States and Canada accessed Facebook every day, down from 185 million in the previous quarter. The company usually looks at monthly active users, in part because the figure is larger. In the fourth quarter of last year, about 239 million people used Facebook in those two countries.

Since about the end of 2012, that number has grown slowly; before that point, it grew rapidly.

The United States and Canada are home to about 358 million people, suggesting that Facebook is used at least once a month by about 66.7 percent of them. That matches data that Pew Research Center released earlier this year, which pegs the segment of U.S. adults who use Facebook at 68 percent.

So it’s safe to say that the number of people who use Zuckerberg’s flagship product is about 221 million people, almost equal to the population of the 16 largest states in the country. There are representatives from 36 states on the Senate Commerce and Judiciary committees who will hear from Zuckerberg on Tuesday. In total, they represent about 237.5 million Americans, about 16 million more than the number of Americans who use Facebook.

But Facebook isn’t only Facebook. Instagram and WhatsApp also are part of Facebook’s empire. While there are probably relatively few people who use those applications but not Facebook, there are certainly some. Pew’s data suggests that 114 million people use Instagram and 71.7 million use WhatsApp. Between those two applications, finding 16 million non-Facebook users doesn’t seem impossible.

While Zuckerberg’s constituency is larger than that of any of those people who will be questioning him, his constituency doesn’t look like theirs. Last year, Pew assessed the demographics of the users of various social-networking platforms, including Facebook and Instagram.

Users of both platforms skew much more heavily female than the general population. More than half of Instagram users are younger than 30; two-thirds of Facebook users are younger than 50. There is also a fascinating split on race: Most Facebook users are white, but most Instagram users in the United States aren’t.

This, as we’ve noted before, is the other weirdness surrounding Zuckerberg’s appearance. In addition to being interviewed by people with smaller constituencies, he is going to be interviewed by people who don’t look much like his constituents. It’s likely, in fact, that members of Congress are significantly less familiar with the Internet generally than are most Americans; it certainly seems to be the case that they would be less familiar with Facebook or Instagram specifically.

One more complication: Zuckerberg’s constituency isn’t only Americans and Canadians, of course. Facebook has more than 2 billion monthly active users around the globe. He is, in a loose sense, the leader of the largest citizenry in world history. The result is a bit like President Trump sitting down with a city council in Arkansas to be quizzed about how his policies affect people in Council Districts 4 and 5.

Well, if people in those districts counted as residents if they visited at least once a month.