Value Investing is all about finding market inefficiencies.

Below is a chart depicting Best Buy's annual return on invested capital (ROIC) contrasted with its stock price:

While ROIC has been predictable and consistently range bound for the last several years, the stock price has been anything but. It seems hard to believe that the market is efficiently pricing this security when its price can fluctuate wildly in relatively short periods of time while the company itself generates predictable earnings on capital. For example, if the company is worth X amount in early 2000, how does it become worth just one quarter of this amount 3 months later, and then three times this amount six months after that?

http://www.dividendgrowthinvestor.com/2009/04/value-investing-is-all-about-finding.html