If we were all totally logical and could separate our emotions from our investment decisions, then, fundamental analysis the determination of price based on future earnings, would work magnificently. And since we would all have the same completely logical expectations, prices would only change when quarterly reports or relevant news was released. Investors would seek "overlooked" fundamental data in an effort to find undervalued securities.
The hotly debated "efficient market theory" states that security prices represent everything that is known about the security at a given moment. This theory concludes that it is impossible to forecast prices, since prices already reflect everything that is currently known about the security.
