I found this somewhere years ago and saved it. It was written by Gregory M. Ellis, with the Department of Economics at the University of Washington. If your highest level of reading, like mine, is the Daily Racing Form and Jack Reacher novels, then find a phd. somewhere and have him/her explain it to you. Buried in all this arcane writing, however, are a few nuggets. I won’t show them to you; you’ll have to find them yourself, like I did.