This paper investigates the influence of hedging on firm value and stock return exposures in U.S. oil and gas industry from 1998 to 2004. Previous empirical results show that the relationship between firm value and corporate hedging activities is mixed. We find that the trend and volatility of oil and gas prices play important roles in the issue. Our results indicate that corporate exposures to oil and gas prices are asymmetric. We also find that gas reserve hedging has significant impacts on firm value when volatility of gas price is high. In conclusion, our results show that corporate hedging policies may add firm values in some special situations.

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In epidemiological studies of an exposure-response association, often only a mismeasured exposure is taken on each individual of the population under study. If ignored, exposure measurement error can bias the estimated exposure-response association in question. A reliability study may be carried out to estimate the relation between the mismeasured and true exposure, which could then be used to adjust for measurement error in the attenuated exposure-response relationship. However, taking repeated exposure measurements may be expensive. Given a fixed total study cost, a two-stage design may be a more efficient approach for regression parameter estimation compared to the traditional single-stage design since, in the second-stage, repeated measurement is restricted to a sample of first-stage subjects. Sampling the extremes of the first-stage exposure distribution has been shown to be more efficient than random sampling.