In reality, since the market is comprised of human beings (albeit aided by some well-programmed machines) volatility can be enhanced by other factors: to wit, if a major holder of a company’s stock decides to sell it off, other investors may wonder if some information asymmetry is being capitalized upon, and follow suit. This mob action could cause further fear and further devaluation of a stock. Conversely, if Warren Buffet decides a stock is a good investment, people can be trusted to follow along. It is clear then that investor confidence (and thus share price) is greatly influenced by word of events. These can be anything from the resignation of a trusted board member, a lawsuit against a manufacturer, or perhaps a massive industrial disaster. For example, over the past six weeks, BP’s (British Petroleum) shares have fallen 15% because of criticism over their lack of progress in the Gulf coast oil spill as well as their revelation that the total cost to date is over $990 million dollars. Company disclosures also drive stocks. For example, if a company warns its shareholders that it will not meet earnings targets, the share price may fall. Notice that these factors can be psychological solely: there may have been no change whatsoever in the underlying company or its earnings. One important measure to mention is that of Price/Earnings Ratio, which is market price of a share divided by earnings reported per share. P/E Ratio provides a good way to estimate the magnitude of speculation’s effect on a stock price: if the price rises faster than earnings, some of the gains may
be due to the emotional factors mentioned earlier, an expression of “irrational exuberance” (to quote Alan Greenspan) rather than more concrete factors. P/E Ratio is also a very important measure in the Dividend Discount Model, which the author of our hypothesis uses extensively. P/E Ratio will be examined more closely later as part of our approach to stock selection. As a side note, investor confidence (or lack thereof) in a stock can be expressed in many ways other than the simple buying and selling of stocks. One important measure is the price of a Credit Default Swap. This will be later discussed with the other securities, and will later become important in discussion of the Gaussian Copula.