Strange but true.

Here's a funny thing - if you write down the length of all the rivers in the world, how many of the answers would you expect to start with the digit 1?  Well there are 9 possibilities for the first digit, so logic suggests that one ninth of them (about 11%) will start with one.  Would you be surprised to learn that the actual figure is just over 30%?  And even weirder - it doesn't matter how you measure them - in miles, feet, inches, metres or whatever, the result will be the same - about 30% will start with the digit 1.  I don't pretend to understand it, but this is known as Benford's Law, which says that for the majority of comprehensive collections of data the most common first digit will be 1, then 2, then 3 and so on in sequence down to 9 being the least common.  Like I say, I don't understand why, but it works.