Back in December 1996, the DJIA stood at around 6400 and NASDAQ at 1300. It was then that Alan Greenspan made his famous remark about the markets's "irrational exuberance." The remark made the markets go down, but not for long. In three years, the DJIA almost doubled and the NASDAQ almost cuadrupled.

Now, Mr. Greenspan made the comment after meeting with a Yale economist, Robert Schiller, who is now predicting that things have to go down even further to reach historical levels. Those ultra-simplified calculations I made a few days ago might turn out not to be too off the mark after all.