There are over 7 billion people on Earth today, and occasionally a bunch of them decide to converge for one reason or another. We’re talking thousands, tens of thousands, hundreds of thousands, or even millions of people in the same place at the same time. As those of us in the United States (and no doubt around the world) have recently witnessed, such events include things like U.S. presidential inaugurations and political marches.

In case you haven’t heard, there’s been a bit of a fracas brewing over the exact sizes of crowds at certain events held in the U.S. this past week. While I don’t want to get into the political aspects of these issues (nor the very reasonable questions about why we’re having these sideshow conversations at all), I feel that it’s important to note that estimating crowd sizes is a solved problem that’s actually pretty straightforward. And it’s relevant to us math fans because it’s really nothing more than a simple exercise in basic math.

So, how do crowd estimate experts estimate crowds? Let’s find out.


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