I forget exactly how it goes, but it's some sort of correlation that noted that examining the file size of a variety of folders and files results in like 1 always being the most prominent number, followed by like 9, and then 2 and then the rest, or something.
It had really interested me a while back, and I wanted to get some more information on it, but alas, I forgot it's name. More than likely, the good people of superuser know the answer.