Power laws

December 19th, 2009

There’s a story on Slashdot today about “a complicated pattern that has to do with the way humans do violence in some collective way“.

Surprise.  The size and frequency of terrorist attacks follows a power law – lots of little attacks, a few big ones.

What doesn’t?  Quoting from http://en.wikipedia.org/wiki/Pareto_distribution:

  • The sizes of human settlements (few cities, many hamlets/villages)
  • File size distribution of Internet traffic which uses the TCP protocol (many smaller files, few larger ones)
  • Clusters of Bose-Einstein condensate near absolute zero
  • The values of oil reserves in oil fields (a few large fields, many small fields)
  • The length distribution in jobs assigned supercomputers (a few large ones, many small ones)
  • The standardized price returns on individual stocks
  • Sizes of sand particles
  • Sizes of meteorites
  • Numbers of species per genus (There is subjectivity involved: The tendency to divide a genus into two or more increases with the number of species in it)
  • Areas burnt in forest fires
  • Severity of large casualty losses for certain lines of business such as general liability, commercial auto, and workers compensation.
  • I could add a bunch more, but won’t bother.

    Why is this considered news?  Why does it get published in Nature?  If terrorist activity didn’t follow a power law, I think that would be interesting enough to merit publication in a prestigious journal.  But this?

    Is it just me, or is the quality of editorial work in science journals dropping?  I constantly see papers in Science and Nature that make the most basic scientific mistake possible – confusing correlation with causality.  And then the “quality” press such as the New York Times and the Economist pick it up and repeat the same nonsense.

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