An Approximation for Convenience Yield in Commodity Futures Pricing

The pricing of commodity futures contracts is important both for professionals and for academics. It is often argued that futures prices include a convenience yield and this paper uses a simple trading strategy to approximate the impact of convenience yields. The approximation requires only three variables, underlying asset price volatility; futures contract price volatility and the futures contract time to maturity. The approximation is tested using spot and futures prices from the London Metals Exchange contracts for copper, lead and zinc with quarterly observations drawn from a 25-year period, 1975 to 2000. Matching Euro-Market interest rates are used to estimate the risk free rate. The convenience yield approximation is found to be both statistically and economically important in explaining variation between the futures price and the spot price after adjustment for interest rates.