You have a good point but remember that there are other factors that affect stock price completely external to the company -- the biggest one is interest rates.

You have a good point but remember that there are other factors that affect stock price completely external to the company -- the biggest one is interest rates. Also, external happennings in other companies such as competitors, purchasers, suppliers have an impact on your company. So those should technically feed a model some factors (and in fact they do at hedge funds.)