IN MAY 2000, shortly after what would prove to be the top of the great bull market of the 1990s, a conversation between Federal Re- serve Board chairman Alan Greenspan and an aide was reported in the Wall Street Journal. The subject was Greenspan's seeming preoc- cupation with the stock market and the impact the market had on Federal Reserve policy decisions. "I could readily stop talking about the stock market," Greenspan admitted to his aide. "But if I do, I will not be explaining how the process is working... There is no way to understand what is going on in this economy without reference to [stock] prices."