There is always risk in any stock traded, no matter how predictable a stock can be or how much research has been done on the stock. Risk on a stock is divided into two parts. There is market risk and specific risk. These two risks are very different. The differences between the two will be explained.
Market risk is risk that can not be diversified away. Market risk can also be referred to as systematic risk. This form of risk refers to matters that are out of the investors control. For example, changes in a stock price due to changes in the stock market. All forms of securities have market risk. This includes, bonds and stocks. Market risk is a mixture of the market, inflation rates and interest rates. For example, if the market suddenly increases, most stocks increase in value as well. However, if the market suddenly decreases, so does the value of the stock. These three factors can not be avoided by any investor. It effects everyone participating in the stock market. Thus, market risk can in no way be diversified away.
Specific risk on the other hand can be diversified away. Specific risk can also be referred to as unsystematic risk. Specific risks are risks that are unique to a stock. It includes business and financial risk related to the stock. As well as that, liquidity risk. The amount of specific risk can be reduced through diversification. An example of specific risk is, say news about a specific stock, where there is a strike by the employees in the company where there are shares you hold.
There is a system that is able to differentiate from market and specific risk effecting any particular stock. This system is called the fama-French tree factor model. It differentiates between the two risks by using three factors. Firstly there is the book to market ratio. Secondly there is the magnitude of the firm. Lastly there is the market portfolios return.
Firstly, the ratio referred to as the book to market ratio simply is the estimate of the companies worth divided by the magnitude of the firm. Secondly, the magnitude of the firm is brought about by the shares price times the added number of shares the firm has in the market. Thirdly, an index like S&P 500 is where the return on the market portfolio is retrieved from.
Under the fama-French three factor model, market risk is classified as the book to market ratio and the magnitude of the firm. This means, that for market risk, a higher amount of returns is expected. This is because market risk is out of the control of the investors and they are unable to diversify it, thus higher amounts of returns are expected. Specific risk is everything else. This form of risk can be diversified by investing not only in one stock but in many different company stocks.