 How many people attended the inauguration of Donald Trump? This was the largest audience to ever witness an inauguration, period, both in person and around the globe. It should be a simple question, but it isn't. Aerial photos showed a much smaller crowd than in 2009 or 2013. And while everyone agrees Trump is exaggerating, I looked out, the field was, it looked like a million, a million and a half people. no one seems to be sure exactly how much. The good news is we've been estimating the size of crowds for a while and we've gotten pretty good at it. The most popular tactic is called the Jacob's method. You take a small section of the crowd and you use it to calculate the average square feet per person. If you can reach out your arm without touching anyone, that's about 10 square feet per person. If you're packed in shoulder to shoulder, that's closer to five square feet. And if you're in a mosh pit, we're closer to two and a half square feet per person. Once you've got an average density, you apply it to the area the crowd takes up. So if you've got a loosely packed crowd that covers half the area of the National Mall, you end up with a pretty good idea of how many people are there. Of course, the experts do it with a lot of different density estimates and a lot of different regions of the crowd, but it boils down to the same tricks you use to guess how many jelly beans are in a big glass jar. You know how big a jelly bean is, so how big is the jar? Most experts say Trump's crowds were around 600,000 people, which is a lot of people. But when Obama took office, he drew a crowd close to 1.8 million, three times larger. Of course, not everyone agrees with the math. The Trump camp argues that the white tarp on the ground caused crowd counters to underestimate the density. And with political rallies, there's always a clear reason to second guess. The organizers of the Million Man March in 1995 actually threatened to sue the National Park Service over its crowd estimate, which pegged the crowd at 400,000. In response, Congress barred the Park Service from providing crowd estimates, just to spare them the political outrage. So this is an old tactic, but with Trump, this kind of active destruction of information has really heated up. You're saying it's a falsehood, and they're giving Sean Spicer, our press secretary, gave alternative facts to that. Instead of mathematical crowd estimates, we rely on less reliable sources, like metro ridership. It's not as accurate, but at least you can't argue with it. You see this dynamic in a lot of places, discussions of climate change, voter fraud, even immigration, issues that are a lot less clear-cut than comparing crowd photos. The problem is, we've gotten so good at discrediting facts and erasing truth, that we can't even say one crowd is bigger than enough. I should end on, one crowd is bigger than enough. I'm Jerry Blank. Okay, yeah, yeah, yeah. I'm Jerry.