"Trading is a zero-sum game when measured relative to underlying fundamental values. No trader can profit without another trader losing."

"On any given transaction, the chances of winning or losing may be near even. In the long run, however, winners profit from trading because they have some persistent advantages that allow them to win slightly more often than losers win."

If you are expecting to win more than "slightly more often", or if you believe other traders who claim that they do, you might want to read this interesting article by Lawrence Harris, Professor of Finance, University of Southern California.

To view the entire PDF document, click here:  Zero Sum Game