Quantitative Risk Management: A Practical Guide to Financial Risk, + Website

1.4 Systemic versus Idiosyncratic Risk

There is an important distinction, when thinking about risk, between what we might call idiosyncratic risk and systemic risk. This distinction is different from, although conceptually related to, the distinction between idiosyncratic and systemic (beta or market-wide) risk in the capital asset pricing model. Idiosyncratic risk is the risk that is specific to a particular firm, and systemic risk is widespread across the financial system. The distinction between the two is sometimes hazy but very important. Barings Bank's 1995 failure was specific to Barings (although its 1890 failure was related to a more general crisis involving Argentine bonds). In contrast, the failure of Lehman Brothers and AIG in 2008 was related to a systemic crisis in the housing market and wider credit markets.

The distinction between idiosyncratic and systemic risk is important for two reasons. First, the sources of idiosyncratic and systemic risk are different. Idiosyncratic risk arises from within a firm and is generally under the control of the firm and its managers. Systemic risk is shared across firms and is often the result of misplaced government intervention, inappropriate economic policies, or exogenous events, such as natural disasters. As a consequence, the response to the two sources of risk will be quite different. Managers within a firm can usually control and manage idiosyncratic risk, but they often cannot control systemic risk. More importantly, firms ...