Efficient Market Theory is one of the Investment Theories, and the theory postulates that at any given point of time the prices of securities being traded in a stock market or any other financial market fully reflects all available information and data. People buy securities thinking that the price shall move up, and they sell securities thinking that the price shall go down. Now, according to Efficient Market Theory, as the prices fully reflect all the available information, any price movement upward or downward is a matter of luck. However, like many Investment Theories, the Efficient Market Theory has also its plus and negative points.