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Counting Crowds

April 8, 2003

A public radio commentary

In Romeo and Juliet, Shakespeare asked "What's in a name?" Concluding that "a rose by any other name would smell as sweet." This may be true of a name, but it isn't true of a number.

For example, an anti-war protest doesn't smell nearly as sweet if 50,000 people march instead of a half million. At a recent demonstration in Washington D.C., the Capitol Police angered the march organizers by estimating 50,000 protesters, when the organizers claimed a half million. So, who's right? The answer is "we don't know" because no one is really counting.

In the past Congress mandated that the Park Service carefully count the number of people at every event at the Mall. But in 1993 the Park Police estimated Louis Farrakhan's Million Man March at 450,000 - a very impressive number - but still Farrakhan threatened to sue. Very quietly, in the next appropriations bill, Congress banned the Park Police from counting at all.

Now it would seem a simple thing to count people, but it isn't. For example, the wrong thing to do is stand in the crowd and look around. When surrounded by throngs of people, most counters will estimate a crowd of 20,000 to be two million.

Instead, you must first make a careful measurement of the area to be occupied. Second, as the rally occurs go into the crowd and measure the crowd density, that is the number of people per square foot. Typically in a subway during rush hour, it'll be about two and a half square feet per person, although crowds thin out quickly to five square feet per person. Third, use an aerial photograph to capture a snapshot of the crowd and to see how much of the area is filled. Using the photo and the crowd density, you can estimate the number of people.

The problem, though, isn't with the method, its that the organizers don't trust the counters. But there might be a way around this.

At a recent anti-war march, the San Francisco Chronicle added a new twist to crowd counting. They used crowd density and an aerial photograph to calculate a number for their news reports. But then they put the high resolution aerial photo on the web, and said to their readers: If you don't like our estimate, print out the photo and count each and every soul yourself.

But before you do this, I'd advise you to keep in mind that the actual number might be a red herring. Clark McPhail, a sociologist who is a crowd expert, warns that the number might not be as important as exactly who is attending.

He notes that the 1970s anti-war protests became effective once middle America started turning out. "It was," said McPhail, "when middle-aged, middle-class folks, and doctors and lawyers" turned out that public opinion began to change."

Copyright 2003 William S. Hammack Enterprises