In the last two decades, the use of derivative contracts by firms has increased sharply. Surprisingly, although data on derivatives usage are more widely available, the empirical evidence on the effects of derivative use on firms’ risk and value is still mixed (despite the fact that anecdotal evidence on its detrimental effects is widespread). For example, using a sample of firms that initiate derivative use, Guay (1999) finds that the total risk, idiosyncratic risk, and risk exposures to interest rate changes of these firms decline, but he finds no significant change in the market risk of these firms. In contrast, Hentschel and Kothari (2001) find that the difference in risk for firms that use derivatives is economically small compared to firms that do not use them. Allayannis and Weston (2001) present evidence that hedging foreign currency risk is associated with large (approximately 4%) increases in market value; Graham and Rogers (2002) find that hedging can add an economically significant 1.1% to their market value by allowing firms to increase their debt capacity. However, Guay and Kothari (2003) show that the magnitude of the cash flows generated by hedge portfolios is modest and unlikely to account for such large changes in value. Consistent with this, Jin and Jorion (2006) use a sample of oil and gas producers and find insignificant effects of hedging on market value.
One factor that affects the interpretation of these results, and may generate some of the differences in these studies, is endogeneity. That is, a significant difference in the risk measures of hedging and non-hedging firms could be due to omitted control variables that determine firm risk and risk management; alternatively, omitting these variables may mask important differences among firms that arise because of differences in hedging behavior. Endogeneity also affects the interpretation of results: hedging behavior may be driven by, rather than a determinant of, differences in risk. As a result, riskier firms may hedge so that their (after-hedging) risk profile is indistinguishable from inherently less risky non-hedgers. The papers cited above use different approaches to control for endogeneity. Some authors use econometric procedures such as simultaneous equations to account for this problem (see, e.g., Graham and Rogers (2002)). Others choose samples to mitigate selection bias. Jin and Jorion (2006), for example, control for any significant difference in the hedging propensity of firms across industries by examining firms in a single industry. By examining only firms that initiate derivative use, Guay (1999) uses the same firm prior to derivative use as a control. Of course, although these choices reduce selection bias, they also impose constraints on the data, beyond the usual ones of data availability.