One perhaps counterintuitive aspect of the determination of expected returns with the CAPM can be illustrated with a simple example. Consider a firm engaged in oil exploration. The return (denoted RA) to the shareholders in such a firm is very variable. If oil is found, the return is very high. If no oil is discovered, shareholders lose their entire in-vestment and the return is negative, The stock’s total risk level is very high. However, much of the variability in return is generated by factors independent of the returns on other stocks (i.e., the return on the market), This risk is unique to the firm and is there-fore unsystematic risk. Since the stock’s return is not closely related to the return on the market as a whole, it contributes little to the variability of a diversified portfolio. Its un-systematic risk can be diversified away by holding large portfolios. Nevertheless, the costs of exploration and the price of oil are related to the general level of economic activity. As a result the stock does contain some systematic, market-related risk,. Most of its total risk is unsystematic risk, however, associated with the chances of finding oil.