International hedging under concurrent risks of input/output prices and exchange rate : The case of Korean oil refinery

摘要

This study develops an international hedging model which accounts for the multiple risks of input and output prices and exchange rates. Considering a fixed production technology, we formulize simultaneous minimum variance hedge ratios, which reflects inter correlations among prices. To utilize the dynamic nature of prices, time-varying conditional procedures are specified to estimate the relevant variance and covariance matrix. The time-varying representations of the variance and covariance matrix are statistically appropriate, in general. The separate hedge ratios are similar to the simultaneous hedge ratios for alternative procedures. The ex post hedging effectiveness indicate that there are substantial reduction in the variance of returns for all the procedures. The contribution of foreign currency futures is minimal due to the low correlation between commodities and exchange rates. Based on the traditional definition of hedging effectiveness, the time-varying conditional procedure provide little gain to the hedgers over a constant procedure in terms of the mean and the variance reduction. However, the performance of conditional procedures could be improved by accounting for the potential problems: mis specification problem, inappropriate definition of hedging effectiveness, and conflicts between theoretical derivation and estimation of hedge ratios. (author). 39 refs., 6 tabs.