When I started Dow Theory Letters in 1958, I worked with three items: the Dow Jones Industrials, the Dow Jones Transports and daily volume on the NYSE. In those days, volume was running two to three million shares a day. There was no NASDAQ and foreign exchanges were largely unknown. Today the picture is entirely different. We have the currencies, precious metals, commodities, derivatives, and foreign exchanges. The more items we have to deal with, the greater the chances of making mistakes.