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Self Organizing Crowds?

A lot has been written about the 2009 Presidential Inauguration, much of it interesting and inspiring, but I've been thinking about one particular aspect: those crowds! Here is a photo I took as we were leaving our spot near the Washington monument where we'd been huddled for hours with 1.8 million of our closest friends.

The crowd was in a celebratory mood and even though we all wanted to get somewhere warmer (it was still less than 20 degrees Fahrenheit by the time this photo was taken) nobody pushed or shoved or got upset. The spot where I took this photo was unusual in that I could see over people's heads. Most of the time, all I could see was somebody's back.

There were moments when I worried a little and began to think about stampedes. Like that one that occurred in a WalMart shortly after Christmas. In their rush to get to bargains inside the store, shoppers trampled and killed an unfortunate employee.

So, I was thinking about that WalMart as we slowly made our way off the National Mall. Would something as tragic as what happened there happen to us as well?

Fortunately, it did not, and we all got out safe - very, very cold, but safe.

Still, it made me wonder: what causes a crowd to stampede? Are crowds of people self-organizing the way bird flocks are?

I have written about this before on this blog. It's something I think about a lot, as does Prof. Dirk Helbing at ETH in Switzerland. In the next few days I will blog a bit about his work with self-organizing crowds and how he has determined what causes crowds to stampede. His fascinating insights may surprise you! Stay tuned.


  1. The wal-mart stampedes occur because they are organized like athletic events -- only the strongest/wiliest get the super-discounted merch.

    At the inauguration, everyone was going to get where they were going, eventually. There was no huge reward for being first. Plus it must have been kind of cool to be in a big crowd of like-minded people. They're not competitors, they're allies!

  2. Dave - Thanks for the comment. Helbing has also found that the geometry of a setting (for example bottlenecks) can affect whether people stampede. He also says high emotion has a lot to do with whether stampedes, so you are right about that aspect! More about this soon...

  3. Glad to have found you.
    Any chance that you heard the book review related to this topic on NPR today 3/23/2009? Can not find it! Thanks.

  4. Thanks for your question, but I didn't hear the NPR show. Do you know what book it was? I would like to see it, too!


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