Demand and Supply

• Stock prices are a function of demand and supply. As the stock price falls, so does the faith of the market, which can cause the stock to go down in price significantly after the initial fall. Certain investors are invested for the long haul as long-term investors. Other investors are primarily interested in short- or medium-term gains. These investors will likely sell the stock once the stock hits a certain level and down goes the price of the stock even further.
  
  

Credit Risk

• Stock price is also an indicator for credit risk for banks and credit research companies. If the stock price or market capitalization, which is defined as the stock price multiplied by the number of shares outstanding, goes down considerably it can trigger a credit review.
  
  

Under- or Overvalued

• Sometimes stock prices fall due to general market instability or something that is not directly related to the company. In these cases investors will look at this as a buying opportunity. The hard part can be determining if a stock is under- or overvalued. One of the most popular tools for determining value is called the price-to-earnings ratio.
  
  

Company Specific

• What happens when a company's stock price falls depends on the company. If the company is financially weak it may precipitate a sell-off. However, if the company is financially stable it may result in an increase in demand for the stock, which will increase the stock price. While company management is not singularly interested in the price of the stock, it is a major consideration for the board of directors.